Gee, it's a heck of a question. I know there are lots of clumsy things I do because I don't see what effect they will have on others, and the results were the complete opposite of my intentions. So, yes, if I knew at the time how dumb some of the things I said and did were, I'd do differently.
But I wonder if that sort of foreknowledge might take much of the spontanaeity out of life. Perhaps life is interesting and rich, partly because we have to stumble through it blindly.