I think I made a post some time back about this exact same thing, I know what you're talking about. Perhaps you actually became smarter and thus have been more able to perceive your own flaws or be more critical of yourself than you used to? Which is the flipside. Either way, I'm not sure how the issue can be resolved other than to use your brain to keep it in good condition, perhaps throw in some cardio exercise for hippocampal neurogenesis.