Actually a really difficult question as very much about the childhood depends on adults (parents, teachers, ...) around you.

Maybe this one: "The whole bullying situation will not change until you leave school. Convince your parents to let you change schools."

You don't have a learning disability and you don't belong in the special classes. Don't trust anyone that says it will be fixed the next year and go to a different high school when they say the classes you want are filled.

Say no more often

Enjoy life to the fullest as a kid. Adulthood freaking sucks.

Don't get back together with her and don't fucking stay with her into college. She'll just break up with you, again, at Disney... again.

Don't sweat the petty things.

..

..

And don't pet the sweaty things.

Mormonism isn't true, but she's worth it. (not the girl you think I'm talking about, she dumps you while you're on your mission.)

Don't go to college.

Actually do what you want to do. Don't try to please everyone else with your life choices, you're the one who has to live with them.

Start taking your education seriously because it becomes hell afterwards. Forget about being a mechanical engineer and instead focus on software. Start working as a full stack engineer and transition towards ai afterwards

Please die. Thank you.