Just say yes, you can always say no later
How many times have you said 'no' before really considering if something is viable. If it could actually work, and whether it would benefit your soul by doing so. My hand it sticking straight up right now (well I'm typing, but you get what I mean), I am absolutely guilty of this. Almost being on the default with the 'no thanks' setting. It wasn't until a couple of years ago really that I started to analyse my options. Either A) continue to say 'no' to everything and never have spontaneous amazing experiences or B) stay at home and have your own predictable fun. I don't mean to have so of a much depressing connotation to be paired with option B - I'm quite happy doing my own thing if I haven't mentioned, but it would still mean that I'd rarely challenge myself or gently push my anxiety levels in a safe and controlled environment.
So I started to be more relaxed. I ever so slightly relaxed my very rigid walls of socialising and I started to say 'yes' to things. I soon realised that when people said 'oh we should totally do [insert activity] some time', it might not actually come into reality, so there is little point stressing over it. If you like the idea of what they are suggesting (usually always) then enjoy the idea of it. There is no point, then and there stressing about it and how you think you would have a panic attack in the situation, if the chance of it materialising is quite low.
Now with this method there are still moments when things do come into reality - duh, but one has to realise if you are really scared and anxious as it comes around, it's OKAY to say no. Of course it's not ideal, you let friends down and stuff up people's plans, but in the bigger picture of the universe, life goes on. It's about not feeling that life is SO darn serious all the time. That you ALWAYS have a choice, to extend yourself, give yourself a break, or put yourself through a nightmare - up to you.
In the past I have felt somethings to be 'all or nothing' experiences. Making the start feel like the most anxious thing ever because with it holds every little bit of the experience until the end. It's like you can't escape, you are trapped until you are released from the social hold. Yet once again, utter BS. You CAN release yourself from any social situation at any time. 3am from a sleepover - not ideal, but it can happen. You have control and once this mentally computes, you'll feel instantly more at ease. Ahhhhh :)
When we realise we have control over every little aspect of our actions, panic attacks and social anxiety don't seem so inevitable, and that's pretty amazing to realise.