I've mostly had problems in my life dealing with accepting the fact that I'm going to have a sub-average life when I had high expectations for the opposite
when i was a kid, right up through about age 13 I breezed through school with straight a's, never had problems I couldn't easily accomplish, then I started developing a major depressive disorder along with social anxiety. my grades started slipping, I spent more and more time in my room alone, and I distinctly remember right around my sophomore year I failed a class and just couldn't give a shit about school or life, but I hated myself for not being able to care.
several years later I'm doing better, but it's still an uphill battle everyday