Drillers make killers. I should've just drilled and drilled and drilled.
Don't take it, and myself so seriously. I was never talented enough to make inroads on the circuit, let alone be a world champion so there was no point beating myself up about it. I should've just turned up, enjoyed myself on the mats and tried to be better today than I was yesterday.
Be more open minded when I rolled. For the longest time (white through to say, mid blue) I rolled way too conservative. Just stuck very much with what I knew and as such, I never evolved for years. These days, I try (within reason) everything and anything. Keeps things fresh and interesting.
Don't roll with guys that are just way too big. I totally bought into the hype that a little guy can beat a big guy. Yeah it's true... when the big guy doesn't know anything. But if they know something, it's gonna me a long round. Winning battles, losing wars type thing. And you can't come back the next day.
Oh and I guess if I'm being perfectly honest, my instructor was a complete douche. I knew it and most people knew it but it took us way too long to do something about it. It led to us at that time being very closed minded and we burned a lot of relationships with good people who we could train with.