I never seem to be happy with myself, neither mentally nor physically. I can't walk past a mirror without thinking "Why do I have to be so ugly and fat?" And recently I've been feeling like I'm a complete idiot because I'm having trouble in one of my classes. What can I do to make myself feel better about who I am as a person?
If you're so displeased with yourself, both mentally and physically, it's not so mysterious that you're falling into two common cognitive traps: perfectionism and self-downing.
Feeling better about who you are as a person means talking to yourself respectfully and rationally. You wouldn't speak so harshly to your worst enemy. Calling yourself names doesn't help, and only makes things worse. Fortunately, there are some issues you can address to counteract this tendency.
Perfectionism has many aspects, including the valuable desire to "do better," "look better," and generally keep to high standards. So far, so good. However, since even Olympic gold medalists fall short of perfection most of the time, we'd better accept that perfection simply doesn't exist. Striving toward betterment is great. The quest motivates us, and keeps us on a good path for the long run. But the idea that you can and should attain perfection will crimp your style, stunt your growth, and make you miserable. The solution, fortunately, is within your power: Talk gently and rationally to yourself about your goal and give up the need for perfection.