As my kids have gotten older, I've let them find out more about the things I was doing when I was their age, but I try to do it in such a way that they see that it wasn't a positive experience for me so they can't say "you did it, so I'm doing it!" later down the line. "I did this-or-that, and I'm not proud of myself, and I'd be disappointed to find out that you made the mistake that I did."