Practice Philosophy

Practice Philosophy, AKA how to not suck ass at everything you do

This is aimed at speedrunning, but it can really be applied to anything you're trying to improve at.
Everyone learns differently, so I already assume you know what methods work for you.
Most people start off with some good learning habits, but then develop bad ones as time goes on.

I notice people eventually regress into talking about the game more than actually playing it. This is probably the most common sin if you actually want to improve. Just play the damn game.

Also extremely important is to look at your and others' playstyle with an open mind. The only way to improve your game is to change it (by definition), and you're the only person that can change your playstyle. So look without biases or sugarcoats of what needs work, and work on those things. Sounds really obvious on paper, but do yourself a favor and take note of how disappointingly often you notice people commit this sin.

Practice and Performance are 2 completely different environments. It makes sense that it's common for you to nail something in practice and then shit the bed when it's time to do it for the real deal. Practice should be for consistency; keep doing the parts you're going to do in a run, exactly how you would do it in a run. And get as good as possible at doing it the same exact way every time. You're only as good as your average; statistically, if you want to succeed, your safest bet is to improve your average. Being extremely good at one small section doesn't mean shit if you can't execute it in the end.

And the most important for last:
Drop the fucking ego. Everyone can learn from this one as it's the biggest blocker anyone faces. If you prevent yourself from trying new things because you'll fail it at first, just to protect your perceived skill at the game, you're not doing yourself any favors. This is especially true for competitive games: if you want to get better, don't be afraid to take the L, don't turn down a match cuz you might lose, and don't stop while you're ahead. Try new things and stop caring how failing them makes you feel or look.

Also stop fucking calling yourself bad, nobody feels sympathy or wants to hear it.