re: Poker & Playing in the past.
It's human nature to mentally rabbit hunt, but don't ever let it change how you play. If folding in that spot was a good play, then it was a good play, regardless of the eventual outcome.
Also, depending on where you play, I would not get too hung up on it because the cards dealt were different than they would have been had you stuck around. Stars is the only site I know of that uses a set deck, like a live dealer. FT and most every other site as I recall use a constant shuffle RNG that never stops shuffling the cards. So when you take an extra half second to pick your bet size, a few thousand card combinations have already been shuffled past the ones you would have seen had you folded. This is compounded even further by the inevitable change in timing of your opponents' actions upon reacting to your action, resulting in an arrangement of cards that have changed many thousands or even millions of times since you were at your decision point.
Still, I sometimes find myself cursing FT for taunting me on the flop after I've folded, even though I know the cards would not have been the same had I stayed in.
The funny thing is that both Ultimatebet and FT (as I recall) offer a "run it twice" option on some tables, which is obviously just a marketing gimmick for people who like to torture themselves. It can't possibly work with a constant shuffle algorithm for the reasons already stated.