Poker is a strange game. In nearly every other game the only thing that is hidden is your opponents' intentions. In poker we don't get to see our opponents hand until the hand is over, and even then only if there has been a showdown. This often leads to players being overly results focused, they feel like they made a mistake if their opponent had a better hand than they did, or if their opponent had a worse hand but they folded. It is important to analyze a hand, based not on the specific hand your opponent held, but on the range of hands that he is likely to have held based on the information you held at the time. So if you get all in preflop with QQ against a player, it's not that important (when judging your play) what exact hand he held, but rather if you would make a profit against the range of hands he could have. If he is a very tight player whose range is AK/KK/AA then it's likely you made a mistake. If it's a very loose player who will turn up with anything from 99 and AJ to AA then you played it fine.