I had the same thing. I used to chuck the most almighty hissy fits whenever a hill was involved. Including once for our anniversary when the bloke took me to wineglass bay. Very embarrassing.
My problem was that I didn't want people to see me puffing away and think "oh my god, look at that fat chick".
I'm not entirely sure how I've gotten over it, but I think it had a lot to do with the bloke being very supportive and getting me out and doing things. I think also when I started exercising properly (like, going out running with the intention of pushing myself) I discovered that puffing and sweating and struggling is just part of pushing yopurself and it's quite frankly, not going to get you fit if you just putter along without breaking a sweat.
I do have a problem with new situations and being surrounded by people I don't know though. I just have a thing about not wanting to look stupid and wanting to make a good impression. Maybe next time you should try just watching a session first so that you can prepare yourself for the things you will be asked to do, that way it's not such a new thing when you do it.
Just be sure to take it easy and go at your own pace. And be sure to get right back into it.
35kg lost. (November 2005 - October 2006)
15kg gained again (as at October 2010).
Back to the drawing board - Let's do this thing!
"You can't change the winds, but you can change the sails"
"Reach out and take control of what lands in your lap"