It is so tough dealing with rejection

I am in my 20s, and I still haven't found a good way to deal with rejection. When I was younger, I was always told I wasn't welcome at the lunch table or to play with a certain group of people in the playground. In high school, I got cut in sports, turned away from band and student government, and more. I was never end up being the person who gets chosen for anything.

I just don't know how to deal with this being told I am unwanted. I still never figure out how to deal with seeing others being given opportunities and privileges in life I never gotten