Your younger self

If you could write a letter and send it to your past self, what would it say? Would you warn yourself of things to come? Assuage ultimately pointless fears?
I keep thinking of scenarios where i mess with the younger me, only to realize again and again that I am only messing with myself. Wouldn’t it be funny to see that kids stick that in the…. oh wait, no that would suck.
I think of warnings I could send, decisions i could have changed. Ultimately, though, every decision I made, every situation I found my self in, every opinion I formed became part of the foundation of me. If I change something I hate, I will change something I love. Then I won’t be me.
Perhaps I got a letter from the future saying don’t write a letter to your past, you will change things in a bad way. So I didn’t send a letter and rendered the need to receive a letter from my future unnecessary. But somehow the lesson stuck.