I have had anxiety about plenty of friends' trips and often had to push through. I never regretted it, though, and usually ended up having fun.

For me, it's always helpful if I can give myself an "out". So if I'm feeling overwhelmed, I just take a little time to myself and do something that makes me happy or calms me down. For example, I went on a multiday camping trip with a friend and two of the days I just needed time, so she did some hiking and I hung out and read, or went shopping in town, even treated myself to lunch.

If you go and are feeling overwhelmed, can you let your friends know and go back to the hotel and watch a movie or something? You may not even need to have a break, but sometimes just knowing that you can take one is enough to make you feel better.