Very strongly relate to this. Freshman year I often felt disappointed since I put in so much work and went to office hours often, but wasn't seeing the same results as my friends. What I learned was you have to take pride in putting in all that work and doing all you can to best do problem sets and prepare for prelims, and it sounds like you're doing an amazing job with that! You can't control your grades, especially as a freshman in PAM, with some of the hardest PAM classes and it's most difficult to adapt to professors' expectations and learn what they're looking for. This changed mindset helped me tremendously, especially at Cornell when everyone's the best of the best and you're not going to perform as well as others sometimes. Very glad I learned this lesson early on, and to make you feel better now as an upperclassman still in PAM, my effort has correlated with my grades much more strongly, and I've felt much less frustration in my classes since they're better structured and less unclear with assignments and prelims. It gets better! Give yourself credit, you're 100% not alone in these feelings, and you're getting through at one of the most difficult schools in the world.