I've read that predictions on the future made by pessimists end up closer to reality than by optimists. It might make sense to plan for the worst from a practical perspective, to limit unnecessary risks. But on the other hand, people with really low expectations are usually not super happy when something turns out better than expected, they just find something else to complain about.
Being optimistic, without setting expectations so high that you're constantly disappointed, seems to be a more pleasurable way to live your life. Also, the consequences of failure to meet whatever high standards self-critical people put on themselves are rarely as bad as you think before it happens.
I like your way of finding some balance between being pessimistic and optimistic.