What helps you play sports at a very consistent level?

I love playing sports, and I play a bunch of them. Like anyone, I get frustrated by my good and bad days. I’m convinced it’s all mental. What are some useful tips you’ve learned over the years that have helped you? In what sport?

My best tips are get plenty of sleep, keep your eye on the ball or where you are throwing, stay loose, concentrate but not so hard you tense up.

Sounds lame, but I’m serious. For example, in tennis I’ll forget to shift my weight on my front foot for a set, then remember. In golf, I’ll look up right before I hit the ball until I remember to stare at it until after hitting it. What helps you play at a high level consistently, minimizing unforced errors?