Don't take any sh*t from girls at secondary school, it's really not worth the hassle.
Stop listening to pop music, it's SO bad.
Don't ever discover the world of YouTubers and vloggers. They'll take over your life.
Study harder now, and reap the rewards later.
Take up a new sport - it's too late for me now!
Just say yes to more things, it won't hurt.
And remember, whatever seems important at the moment, it isn't. In the grand scheme of the whole universe, that b*tchy thing that person said, or that spot on your forehead, is literally nothing. Life is a gift, and don't waste it.