Why is it I always look back at a decision I made and in retrospect, realize, Dumb, Dumb, Dumb?

Why can't I see this before I make a decision and save myself a lot of time and trouble? I'm talking about financial decisions(which usually really hurt), life decisions, what I call mood decisions(whether I'm happy, sad or angry) and even what am I going to have for lunch(why did I eat the whole thing type decisions). It's not like I'm learning from my mistakes either(although I have learned to be more cautious). Maybe that's the lesson here, don't be rash in deciding and think things through slowly and clearly.