One nice feature of us spiritual travelers is that we tend to know pretty quickly when we have messed up. Once you have identified a path for yourself, you pretty quickly realize when you are deviating. The interesting thing though, often when I mess up, I tend to learn valuable insights about myself - why I am attracted to this dark soul spot in the first place, what consequences it carries when i pursue it, etc.. Most of the time I am actually pretty happy while the universe is throwing -temporarily- bricks at me. I often conclude that this 'mistake' was actually just the right thing for me to do at this point. Mistake, what mistake!
Sometimes I wonder whether we really have a choice. I think about my biggest mistakes and know that, facing the same situation at the same state of development, I would do them again. But certainly not after I have digested my lesson. That's what a mistake does, it changes your personality for good. The only real mistake is the one where you know better, but you still do it. Well, that's kind of dumb, isn't it?