It's less common for us to see the opportunities that we missed. If we fold to a smallish bet when the pot has a big For Sale sign on it, we won't generally count that as a mistake even though we've just given up a lot of equity. We don't usually notice the blinds we could have stolen or the raises we missed. Someone who never put a chip into a pot he didn't win thinks he played brilliantly, no matter how much money he left on the table.
It's hard to see what you didn't do.