By nature, people are self-conscious to an extent. I mean, even the most confident of people have some moments wherein they end up doubting themselves a bit or worrying about some aspect of their being.
"Oh nooo. I feel so uglyyyyyy"
And then all we normal people are sitting back here like "Bitch, puh-lease". But we can't really help it. We get self-conscious, we sometimes compare ourselves to other people, and generally overthink things so much that the end result leaves us just wanting to curl up in a fetal position, cry our eyes out and die, lest we suffer more of this horrible existence.
Growing up, I was bullied all the time and as a result, my self-esteem plummeted. I hated looking at myself and I was usually always by myself being a loner and stuff. On the really bad days I remember I would hole myself up in our school's dingy bathroom and bawl my eyes out.
"Why do eight year olds have to bear this much pain?Boo hoo"
While being bullied really sucks, the key is to not let it affect you. Kids can be horrible, brutal creatures. One moment they're all kinds of adorable and the next they're very capable of being devil spawn. Truth is, no one really thinks about you or notices you as much as you believe.
Don't flatter yourself, kid.
And while that sounds kind of really depressing, just think of this: that single incident when you slipped on the sidewalk and landed on your butt that you obsessed over for days on end? Everyone who witnessed it forgot about it within the next minute. Feeling self-conscious that everyone's looking at you? Should you have worn that other top with these shorts? Do these pants make you look fat? Do you have something in your teeth? DAMMIT WHAT DO YOU LOOK LIKE RIGHT NOW? SOMEONE ASSURE YOU AND TELL YOU YOU'RE GORGEOUS! Big surprise: everyone is too preoccupied with their own crap to really notice things like that. We're so narcissistic that we always try to skew things to fit our twisted perception that we are the center of everything.
In reality, we magnify things so much that it affects us; our thinking, our performance, etc. The key is simple, really. Don't overthink things. Sure, I still get self-conscious sometimes, but knowing that no one really cares as much as I think they do grounds me. We're all awesome in our own right and in the end, we ourselves have to believe that since that's the only opinion that really matters.