I think I'd thank my past for self for steeling against criticism, and not letting anyone take the joy of creating art away from me, no matter what my skill level.
To just keep on truckin' on.
I also thank my past self for keeping an open mind, and not ignoring the advice of others. For not assuming I knew everything, and that I could learn from others, even if what they said my not apply to my goals. To this day, it takes time for advice to click, but I try to not completely ignore it, until the slow cogs finally move and send those messages where they need to go to get me to figure what what was meant XD
I want to thank my past self for writing a little note in fading graphite, on lined paper, folding it up, and pouring candle wax on it, and unceremoniously shoving a pewter dragon head into the wax...only to open the following year so that I can think back today—two years from turning 40—and reflect on that message I'd written back in 5th grade:
"Don't forget you wanted to be an artist. Don't forget you wanted to do art. Keep drawing. I will be disappointed if you don't."
*disappointed was spelled wrong. I clearly remember that. I am awful at spelling.
sidenote
(I'm paraphrasing, because in one my moves I lost this piece of paper. But I remember it.)