I'm definitely not tempted to mess with any of the big obvious decision points in my life, but I do occasionally think wistfully about going back to a certain bookshop, finding the version of me who's about to decide not to buy a book, and tell him he totally should. I probably wouldn't actually do it if I had the chance, though: who knows where it might end? And anyway, I don't actually remember what date it was.

James H Schmitz once wrote a short story called "Would You?", in which the protagonist is presented with an opportunity to alter his past. It includes a lot of safety features, including being able to preview any proposed changes to see what consequences they would have -- and he still decides, in the end, that he wouldn't.