Don't worry about it. I've been through this countless times as I'm sure all creative people have. It's depressing, but the other side of the coin is that this is the thing that gives you confidence in the right ideas. The trick is to keep doing what you're doing and wait for the time when an idea comes along in which you can't identify any fatal flaws and that you don't seem to be able to stop thinking about. Don't bank on having a perfect idea, all will require adjusting and lots of persistence to implement. Just like natural selection the good ones will hang around. Have patience, wait for these ones. If they have been destroyed by weeks, months or even years of critical thinking then they're the ones to lean towards.