Bill has some great thoughts on this (as usual). Backpacking is a great activity, but it can be easy to get discouraged if your first trip or two turns out badly. As Bill suggests, start out with simple trips, even car camping with short day hikes. Don't try to prove anything, to your friends or yourself. This is supposed to be fun, not a survival course. Sure getting in shape is a good idea, but that can be done slowly. Don't let your friends push you into more than you can handle. I've gone winter camping just a few miles from the trailhead, but the experience was the same as if I was in the middle of nowhere. It's all relative.