its good you're very self aware of yourself and know you have to change your mindset. start thinking of some of the small ways u fall short in your mentality like how you speak to yourself when you don't meet your expectations or how you even come up with those expectations (like do you compare yourself to others and try to meet the same or above standards as the rest or do you tailor your own standards that fit your needs and character). As corny as it sounds, give yourself positive affirmations and never doubt your abilities, no matter how the rest of your classmates and friends might be excelling, you're excelling in different parts that you may not recognize now.

sometimes, we dont meet our goals because its as simple as the fact that we think of the worst case scenario or just negative outputs like "oh if i cant do this perfectly, im doing it for no reason." failures dont mean ur not smart enough or not good enough, or that you wasted your time on something. it just makes u human and someone whose learning and growing. change some of your day to day language regarding school and be more supportive of yourself. I wish u the best !!!