Here's my thoughts on this:
Anytime I offer a perspective or advice, I'm aware that what I say could be looked upon with the attitude, "Of course! We know that!! But, we can't DO that!!" And that would likely be true for anyone asking for advice or feedback here, because if you are doing the therapy at some point in time after someone else (I mean to say that if you have been doing the therapy for a shorter period than someone who has been doing it longer), then you haven't had as much time for the therapy to sink in - obviously. So whatever I (or anyone) say to someone starting out with the therapy, might sound simple or condescending. I always hope that is not the case. I hope instead that what I might say, or someone else here who has longer experience with the therapy - I hope this experience helps encourage. You already "know" these rational things. So knowing the answers doesn't change you. But, the longer you do these strategies (the therapy daily), the easier it will become. So, it does take time. I hope that from our comments, you gain some amount of relief from the fact that over time, if you continue in this direction, things will get "easier" for your brain to accept and do.
You mention "stress". So yes, I think doing the therapy involves some amount of "stress" because you are trying to get your mind behave in a new way, to form a new habit. Change could be described as some amount of "stress". In this case, I hope we can veiw this stress as notifying us that we are going in the right direction. We choose not to follow the habits that come easier, which would continue in a social anxiety way, if we let them.
I feel that anxiety, not just social, involves some amount of over-thinking, brain activity. So, in some ways, we tend to be thinkers. You mention "obsessing" and "over-thinking". Yes, this is what we do. This is also why we are sensitive now. Think about the fact that being sensitive to something involves some amount of over-thinking it. If you didn't think about something, you wouldn't be prone to being sensitive about it. So, this gets us back to the thinking mind-games we are so good at. We are experts at driving our brains in nonsense circles and over-thinking things to the ends of the earth, all the time, everywhere. That is what we're changing here. You know that already. It will take time and practice. Until then I can say to try to let that go. But when I say that, you could reply "HOW!!!!!" Because I couldn't just let that go either before I did therapy, and while I was doing therapy at first. It has been a gradual process that I formed through the therapy, and over time - repetition.
Having spoken with so many members here, people who contact SAI, and just based on my friends in the group and myself - there is, quite unsurprisingly, a tendency for people like us with anxiety to over-think everything, so that we also over-think the therapy, and over-think the strategies, and over-think the over-thinking. The same social anxiety tendencies we are working to overcome are the tendencies which keep many from doing the therapy. These tendencies might get in the way of people letting go and just doing the therapy. I try to encourage people to treat any "is this an ANT..." thing or thought with the simple idea that "yes, it is, so treat it like one, don't question if it is or isn't, and work on dropping it there." Work on dropping the perfectionism, the over-thinking of the therapy and the over-thinking of the thinking, because it gets us nowhere, and worse - it gets in the way of the therapy that you need to get out of this downward spiral.
Having said that, I know how hard it is to do this - to stop the over-thinking. To that, I come back to what helped me - and that is to know that you need time. Naturally, for this biological process to change, you need time, and that at least gives me some form of comfort that maybe allows me to let go, and to know that if I continue doing the therapy daily, despite what I may feel now, that in time, this feeling will change.
Of course I want to get cured as fast as the next guy. Of course I want to never feel anxious again ever in my entire life - but all that starts the loop again. The loop of pressure, and some amount of internal mental resistance. So resistance is persistance, and those thoughts aren't going to ultimately help me at all.
So in time the individual therapy strategies will start to be stronger for you. And then over time, they start to come together more, so that it's not just one idea, but the "whole" of the ideas that you can start to live your life from. And to tell you now that you would feel all of these together, that you can successfully employ each strategy, well I think that is not naturally possible for any human being. Over time and continued repetition, it does become more possible for you.
I'd like to encourage you to try to let go. Even though you don't feel it's possible, still try. I'd like to encourage you to try to cut the over-thinking. Even though it doesn't feel like you can or it feels hard, you treat that like an ANT too and just keep reinforcing the stoppage techniques. I encourage you to try to see any self-pressuring expectations and to back away from them, to remind yourself that perfectionism here is not your friend. These are the tendencies I see in people who keep fighting the therapy, who are not letting it help them. So try to put those ideas away on a shelf, like you would an ANT, and not worry about that book. That ANT or that tendency is a natural thing, and you've placed it over there on another shelf in the "library" but you choose to read other books, to enjoy other books. Don't keep reading the same dark book over and over again and getting nowhere. There is no reason to fight it, but just choose not to pay it any mind. Again, this will take time. But you make that choice right now, in the present, each and every time. So, encourage yourself to make the right choice for you now.