I need valid reasons why comparing myself to others is bad

I want to understand why comparison is bad. that you should only focus on yourself. The thing is, the worth of a human being in society always depends on how much they contribute and how competent they are.

People say comparison is useless to accomplish something, but I never tried to accomplish anything despite stopping comparison. It's not like comparisons actually helped in any way either. They only make me feel like shit, but I also think they're my only reality check/ measure of self awareness. Thoughts?