If you can't be yourself around someone and if you can't feel comfortable expressing yourself around them then they are not your friend and you are better off keeping them at arms length.
Surround yourself with people that make you feel safe and who like you for who you are. People who respect your boundaries, people who lift you up instead of try to bring you down, people who don't try to push you to do things you are not okay with.
It's okay to be different. If anyone tries to tell you otherwise then they are lying.
Know when to walk away/switch off of the internet.
There is a LOT of information that gets thrown around, so much so that its easy to get overwhelmed. Taking a moment to disconnect and focus on your immediate surroundings- be it your country, state/province, city, etc, can do wonders for your mental health.
Think about what you post online. Not only because it could hurt someone, but you may cringe at your younger self. Facebook Memories makes me cringe sometimes, not because what I said was bad, but because it was immature and childish (because I was immature and a child). I'm rarely on here anymore, but I'm kinda glad all my posts are hidden, as many of them are from when I thought I was "mature for my age" Now I understand in my mid-20s that I'm still immature.
Another thing: it may be a good idea to either go into college without a major, take a gap year, or skip college altogether. Many kids (in the US, at least) are told that the only way to avoid flipping burgers at McDonalds for their whole life is to go to college, which is not true. There's apprenticeships as well, and even flipping burgers at McDonalds can lead to a lucrative career in the restaurant industry. Many teenagers have no idea what they want to do at 18. I thought I wanted to get into computer science, but I found it didn't keep my focus and I was really just attracted by the money. 7 years into my bachelor's degree and I just realized I'm not sure if I even want to code. I didn't realize this earlier because I was more concerned with getting through college, but I recently realized I haven't even had an internship yet. At this point, I'm sticking with it because I literally have 5 classes left, and just having a degree helps. I can still get a job in a tech field, but the sad part is I could have done that with an easier degree.
Please call me hooky.
I no longer go by this name anywhere else and it just confuses me.
Don't give up on something because you're not immediately good at it, and also learn the difference between a bad day and a genuinely bad situation. Take something like piano. The second piano starts getting hard and gets frustrating, don't automatically throw your hands up and be like "I'm not good at piano! I hate piano! I don't want to play ever again!" Stick with it, and one day you'll look back and the thing you were so sure you'd never master will be second nature to you, and you'll be glad you kept with it.
I make mistakes, but my own,
and it frees me.