You know, it's funny. Every single time I work on any project in which I do something I've never done before, no matter how small that something is, I end up reinforcing and relearning things that didn't stick the first time, or stumbling upon a new idea that challenges my idea of programming. It shocks me every time. It makes me want to always be doing something challenging.
My problem is that I struggle to find ideas that excite me enough to want to build them. It wasn't always like this, but recently I've started to feel this way. I thought it might be distractions, so yesterday I went and sold my Xbox and all my games to GameStop to get that out of the way. So far it hasn't been too much help. Funnily, when I do find an exciting project, I can go for weeks. It's harder to stop than start at that point.
I guess the best thing people like myself can do is just be completely honest. If the project seems like a cool idea, but it doesn't make you want to jump up and start working on it immediately, then it's either not cool enough, or not something you're excited by. In either case, move on. It's not worth your time. It'll be another incomplete project to make you hate yourself. I think in my case it might be good to break from game programming for a bit and experiment in other things for a while.