One of the worst feelings ever is when you look into the mirror and you don't like what you see. Your nose could be sharper, your hair could use a little bit of trimming, and your body, oh god your body. Let's not talk about that. You think on your person. You're uncharismatic, socially awkward, you have no talents; you're inadequate. Everyone else is going on better than you are.
But that's you talking to yourself in the mirror. After years of growing up in that honestly beautiful, god-given vessel of yours you've learnt how to efficiently filter out most things good about yourself. Wait, scratch that, most things about yourself, because more often than not there's more good things about yourself than what you're willing to give credit for.
This is a time where you need not be humble. This is a time to be proud of yourself, not to feel inferior to others. You're a dancer, aren't you? Didn't you pick up the guitar recently? Hey, that girl said you were cute the other day. But we tend to forget our own triumphs, giving the merit away to others whom we deem are better than us (whom at this point is practically everyone else, right?). There's a fundamental problem with us people in how we see ourselves. "My flaws + other people's strengths = how much I'm lacking as a person". It's funny when you realise that's how they see you too.
You need to look at yourself the way your friends look at you. When a compliment passes your way, let it digest instead of just dismissing it (but don't let it make your head swell). Take into account that (shockingly) you too actually have something that others envy. Not kidding. Accept what you have to offer, improve on it and take advantage of all those perks. For one thing you lack there's two things you can do better than everyone else, so use what you have instead of wishing for what you don't. It's not possible for someone to be good in everything, but you can damned well try to be the best in whatever you know.
So carry on dancing and practicing for your recital, strum that guitar and sing loud the words of your heart, maybe even approach that girl and tell her you think she's cute too; after all you've got so many things going on for you, you're making me jealous you know.