Why do I always feel that everyone else is smarter than me, but I am the stupidest? What happened?

This is because you have too low self-esteem and low self-identity. You should change this kind of thinking, think about what you can do well, give yourself a little confidence, treat yourself as inferior to others in some ways, and then make more efforts to make progress. Stupid birds fly first, as long as you pay, you will get something.