Most of the time, I'm quite grateful for my crappy (selective?) memory. I think I do pretty well recalling the lessons I've learned (not that it keeps me from making myriad other mistakes, but not the same ones, at least).
No, the past isn't the issue, but that inability to remain in the present, without wishing for a future that exists only in my head. That's just madness. I mean, there's faith and hope and working toward a goal, then there's just escapist fantasy.
As the wise Jimmy Buffet once said, "There's a thin line between Saturday night and Sunday morning."