Although I'd never change any of the experiences I've gone through and things I've learned from them, there are many things I wish I could go back in time to tell myself "Dude, chill. You're great, you're fine."
1. The only beauty that truly matters is the one you see in yourself.
Everyone worries whether their beauty is seen and approved by someone else. If we can't even be our own idea of beauty sometimes, then imagine trying to be everyone else's idea of beauty. You can't. This is why it was so important for me to find what I thought was beautiful in myself and embrace it. Every day is a journey, there's days where I'm not content with something about myself but next day I totally forget about it and continue knowing my self-worth. Now that I realize this, I wish I could go back and tell myself not to worry so much about my belly fat and my frizzy hair. But above all, I would really like to reassure myself that the best acceptance I've gotten is from myself.
2. Bad days, bad times; they happen and they also end.
It's important to understand not everything will go as planned. Plans will get cancelled, people might not understand you, but life happens and we must toughen up during hard situations and see the benefit of them. But the most important thing is to not forget that situations come to an end and the best thing that we can choose to do is to learn from it and grow. How to avoid the situation, how to handle it better next time, and to grow from the situation.
3. Dedicate time for yourself.
I don't mean this as in spending all day in your room sleeping only. I also mean getting to know yourself, your interests, your passions. If you realize you like to draw then practice it, if you always wanted to learn how to roller skate then learn, if you want to play video games all day long then do it! Spend time embracing yourself and doing the things you love, with the people you love too.
I think we're always worrying about others that sometimes we forget to worry about ourselves. Don't forget to make yourself a priority sometimes.