Exercise, specifically following powerlifting programs. It makes me tired so I can sleep without stressing over what I need to accomplish work during the next day. It also makes me crave healthier food. It's a feedback loop, and it makes me sharper mentally. If I skip 1-2 days, I immediately notice the negative effects by the end of the week: cloudy thoughts, less motivation, etc. Powerlifting also gives me goals to work towards; PRs on certain lifts. It's replaced my cravings for MMOs which I've spent too much of my life playing - It's feels like I'm the character and I'm constantly working on improving my real life stats.