I would travel back to grade 10. High school was still a impressionable time for me, so it would be easy if got schooled by my future self hah.
I would tell me
"actually try in class. You're smart enough to be with the nerds but you don't do shit and in your in the burnout classes. Grades actually matter here. You're going to waste a lot of your adult time upgrading your classes because you don't give a shit now. You are not going to lose your burnout friends if you embrace studying and hard work."
And then hit me with a little
"Stop doing drugs, it's easy to think everything going to be fine, because it will be for a long time. But one day, this shit is going to stop being fun, and it's going to take over your life. You don't need to personally experience everything. You're way too young, and more people know what you do then you think. People know your a druggie, dumbass."
Followed up by of course
"Don't worry about mom and dad. Their problems are their problems, not yours. When you move out, you'll realize how little their bullshit actually affects you. Stop arguing with them, you'll never win, and you only get punished. Keep your mouth shut until you are 18 and get the hell out of there."
Almost forgot to mention
"You need to stop wasting time, find out what you want in life, and start pursuing it now. You can be soooo far ahead of the pack if you start early, and it will only help you keep a postive life. You need these things, you've given up on everything you thought you love, and now you have nothing. Find a passion and start now, you little shit"
How am I going to not say
"Dump that girl right now. You're going to waste your prime- freshly adult life with her. She's going to leave you emotionally scarred and you're going to waste thousands and thousands and thousands of dollars on her.
Also sprinkle in some
"You need to learn life management skills. You're kicking a rock during your prime learning period, and you're gunna wonder why the hell you are not prepared for life. It's because you didn't prepare, dummy."
Without overthinking, and rambling on forever, I'd end it with
"You have so much potential. You wasted it all once, don't do it again."