The answers are in the therapy. The answers are in doing the therapy.
Please read this as my sincere advice, and not condescending in any way. I don't intend at all to trivialize or to underestimate how hard it feels, and is, to overcome social anxiety. As I've stated previously about myself - I had the benefit of being able to do the therapy uninterrupted at a certain time in my life, a point where I didn't have a lot of distractions or "heavy" daily responsibilities. I had bottomed out, with nothing else to worry about, so to speak. Perhaps the luxury afforded to such a situation was that I was able to focus on the therapy daily at that time. Also, after I did the therapy series for the first time, completely, I also joined the 3-week intensive therapy group at the Social Anxiety Institute in Phoenix. Now, this was after looking in vain to find such a group in my city, and then in my state. But fairly directly I joined a supportive group here. And it makes a huge difference to be able to work on this stuff in a group that really understands it. I don't know if I could have made the same progress without the help of such a group. The people who write on these forums, the people doing the therapy while still needing to survive daily life and face daily challenges... and those same people making progress and then starting to do behavioral experiments on your own...!! Well, I applaud you because I am not sure I could have done that on my own.
And, ICanDoIt, you are a teacher interacting with hundreds of people daily, DOING the therapy, APPLYING it to life, not avoiding life... So, I applaud you too. It is not easy. I can't imagine being able to do it in your shoes, quite frankly.
Still, I hope to say - the answer is in the therapy. And what do I mean by this? I'll give you an example.
I have had plenty of conversations with people doing the therapy, group members here who are doing the therapy, and seeing changes in their lives, positive changes. They are doing things with more calmness, they are slowing down and doing things they never imagined they could do again. Behaviorally they are out in the world doing things with other group members - "experiments" - and they are doing things just normally on their own which make them feel more freedom again, confidence. These same people may later talk to me about "other" problems, or concerns about a particular thing, or some deeper strongly held belief that they feel like losers in certain situations. And sometimes they might ask me or the other group members how to deal with that. They might look for other therapy or other methods to deal with this "new" problem they're facing/feeling.
It's not new. It's the same stuff. It's an ANT. It's an ANT that the person is not applying the same strategies to. It's an ANT that the person is not using the therapy on. It's an ANT that the person is allowing to roam freely. And if you let that ANT roam freely, it does the same as all the other ANTs that you once did apply the therapy to, and that you did gradually work yourself free of. Usually such conversations involve a lot of beating oneself up, irrational beliefs about self (self-hatred and rejection), fear and therefore resistance instead of not fighting it, and, in general, the expression of all things that run counter to the application of the therapy. It's almost as if the person in this example has done so well and gotten very far, but then stops applying the same healthy techniques to the same issue, and there is no awareness that, yes, indeed, this is still an irrational thought which needs to be treated as such. There is no need to run out and find a new calming technique which makes us feel better short-term, but doesn't effectively change thinking patterns long-term, which is what is needed if you really want to overcome social anxiety and all that this means.
I'm looking at what you wrote. It's tremendously good to know there will be setbacks. Setbacks don't feel good, but you must be aware of that so they don't keep you from getting better. We should not trust our feelings here. Our feelings, as you point out, will involve frustration and defeat. But, the therapy and the way forward is to not trust those feelings. Stop those feelings like ANTs. Don't feed into them. And don't resist them, don't fight them. Frustration is a fighting a feeling really. I dealt with this long after therapy. Wondering when FINALLY I'd stop having such feelings,... When FINALLY I wouldn't worry about XYZ ANT. Gradually I came to the realization that each time I felt that way or had that frustration - that I was resisting, which is exactly what I shouldn't have been doing. To keep the ANT alive and that feeling of frustration alive, yes... then please choose fighting it. And I'm not sure that I had such a great epiphany on it. In talks with friends and while reviewing the therapy, I just became more aware of how I was fighting it, seeking perfection, instead of remembering the paradox and the theme of resistance and persistence. So at that point, finally, when I had those same feelings of frustration, I began to deal with it with the same therapy strategies. "Hold on! Wait a minute. I'm having that feeling of frustration right now, but I don't need to. It's okay to feel this but not to feed into it. It's also okay to have these feelings of frustration. That's human." And often with this rational self talk, it would allow me to stop the thought thread on that, and I would stop the ANT, by not resisting it.
I'm not saying this is easy or automatic. It took me a long time to spot that I was in fact still resisting, that in fact I wanted to graduate to a level of perfection. I never clearly said this out loud to myself, but that was what I was expecting. And only later did I realize this was a belief I had that fed into ANTs and that was not needed. It was very subtle, but also my solution, or my way to deal with it was subtle but effective. And all of that is indeed in the therapy. I just wasn't applying it to my life anymore at that time, which I should have been, but okay, I wasn't. When I woke up to the reality of what was going on, I could return to applying the therapy in an effective way which did help. The answer wasn't in starting yoga or finding a new hobby. The answer was in the therapy.
You talk about losing hope. I also read that you are a teacher and you deal with hundreds of people daily. So, I would suggest to you that at least a hundred times a week you also do a fine job, an okay job, maybe even a great job. In fact no one is noticing your eye contact except you, or at least hundreds aren't. So that means some portion of your life is actually quite normal and quiet successful. It helps to be rational with this. All is not bad. All is not great. We are mostly somewhere in the middle, except for people like us we are probably way better than we give ourselves credit for.
You say, "I don't know how much to give and where to look..." This, in my opinion, is an ANT that needs to be treated like one. I understand your statement and your feeling, because eye contact is an issue for you as for so many people here in the group. But "how much to give" ... "where to look"... this is over-thinking the issue. And if you are over-thinking something, that is an ANT. Once we start over-thinking something natural like this, it becomes unnatural in our minds. There is no perfect answer to how much to give or where to look. There is no perfection. There is no right answer from one person to the other or from one culture to the other. So, we drop it. We stop that thought, we stop the thinking about it. We stop the post-situational ruminating thoughts. That is in the therapy.
"I get nervous, dizzy, headache, muscle tenstion..." Of course you would if you have incessant thoughts and if you use your body defensively like many of us do to avoid anxiety situations. But what is the answer? The answer is not one thing - the answer is slowing down, using slow talk, practicing focusing out, slowing down helps with breathing and helps to lower adrenaline and cortisol (which would help with your anxiety and dizziness), and practicing daily something like the PMR exercise for loosening up the body - which could help with your headaches and muscle tension. The answer is in the therapy.
We cannot practice one part of therapy for one particular thing. Example - I want to be able to order food in public without feeling weird. Or: I want to be able to talk slowly and confidently on the phone while other people are listening to me. Or: I want to be able to be calm when I talk to this person. Or: I want to be able to not worry about my eye contact. That would be splitting up social anxiety into 100s of problems instead of working at the therapy itself which allows one to better handle life skills which then help you handle 100s of situations.
So, there are many things which go into your issue here and every issue people face with social anxiety. Practice ANT stoppage, practice the slowing down techniques, practice loosing the body at home and in situations outside, practice slow talk, practice focusing outwards, practice the coping statements, the deserving statements. Practice the therapy daily. As all of these stengthen, they all help overall and in specific situations like you are facing. To actually give you a smaller key to just deal with this situation would be doing you a disservice. Because it doesn't happen that way.
But also... how do we practice these things? Now this is something we can break down. Practice slow talk by yourself, then with people you feel calm around, and then with others at your work perhaps. Practice the skill when you can, especially before the big "challenge". You do need to practice it before using it "for real". Practice the PMR daily at home, then remember to loosen up your body when you're out in public but not in a tense situation, and keep practicing it and remember to practice it throughout the day. Only if you practice it will you be able to call upon it when you are back in that class looking at 100s of people. If you didn't actually practice it, you'll be less likely to use/benefit from it. Practice eye contact with someone you are comfortable with, practice it at the mall - you could sit and work on being calm and then try to naturally look at people as they pass. You'll find that eye contact is so short and it's even hard to catch someone's glance, but you'll be practicing it. Perhaps first you could sit while doing this, at a point where people walk by. Get comfortable with that and then change it, step it up. Get to a point where you might be standing right in the middle or in front of a larger store opening. It would be as if you are waiting to meet someone, just standing there. People walking around you here would be more likely to look at you, but even then not for long. And you can practice looking at them. Then practice talking to store employees about "nothing" about products, ask for help, ask questions about products. You can have short conversations with these people while you practice looking at them naturally. At the same time you are practicing focusing on what they say, focusing outwards not inwards. This, by the way, is the same set of exercises I do with people here in the local group. We start easier and slowly work our way up. We practice the same thing many, many times until that becomes easier, and then we change it or step it up. It's broken down and then modified as needed. We practice eye contact in other ways also, but this is just one example. I want you to understand how things can be practiced before meeting the monster dead on in the real world. By the time people have done this, there usually isn't a monster anymore, and there never was. But we all need to go through that to learn that for ourselves. Knowing is never the same as believing.
In all of these things - the answer is in the therapy.