1. Consider the leave on your shot even if you miss (in other words don't sell out). I play a ton of eight ball and I'm constantly looking at situations where it makes sense to try a slightly lower percentage shot that leaves the opponent safe vs. a sellout shot that I'm still not sure to make.
2. Control your anger.
3. Don't just roll balls out and shoot them for practice, do a specific drill.
4. Don't shoot without a gameplan (and in particular, don't sink balls if there's no way to run out... leave them on the table so they can help you run out later, and try to maneuver them into better positions)
There's a ton more but it's hard for me to say what I got from a person vs what I got from forums, books, or on my own. Like I have no idea who told me to avoid banks and combos.
On my own, the best thing I ever figured out is to not lie to yourself about how you're hitting the ball, how you SHOULD hit, and what's possible or not possible.
