you can just go for a bit and leave before it all starts getting too much. exposure therapy works.
i used to eat a progesterone before doing outside world things to just give me a bit of the sleepies and stop my mind racing so much. then propranolol if i started getting shaky or sweaty (you're uk right? your gp will probably just prescribe it if you ask) and then half a mirtazapine (it makes you sleepy) as a last resort. and after a lot of work i can now rawdog the world for hours! and you can do it too :)