I can only think of some pretty dramatic stuff...Hadn't revealed much backstory on my MCs yet, and won't happen for a while, but here's a teaser of my two protags:
Alec Tryon to his younger self: "You're gonna do some great things, son. But whatever you do, don't go hunting with Dad..."
And Friar(chicken), to his cockerel self: "You can't win every fight..."
Yeah, there's some past trauma(s) I'm working on. Can't wait until I get to draw those parts!