It sounds like an over simplification, but the key to getting better really is doing it a lot, playing with others, and most importantly having fun and not beating yourself up.
It's really hard to progress when you're down on yourself and worried, it shatters your mental focus, and it's hard to play well when your mind is racing and you're probably tensing up from nerves which is why you biff some of your fills and seize up over all.
I used to get like this, especially when under pressure in music school where you are constantly judged by people who hear everything, but about half way through I had an epiphany of sorts, "Yo me, wait a minute...i really don't care what other folks are thinking of me or my playing, and this is one of my favorite things in the world to do and I'll be damned if im not going to enjoy it, mistakes, average chops and general dumbassedness and all". You miss a break-away layup? Well whoop-de-doo, everybody lives. Nelson from the Simpson's might point and laugh, but he's an ******* so who cares. Did this mental shift make me a virtuoso now? Not even close, but I can hang with most players, I play the way i want and like the sounds I make even with the imperfections, and I love to play every time I get a chance. I'm 35 and still practically run home some days to practice or play.
It's your thing. do what ya wanna do. Check the Lou Donaldson version of that one on youtube for some serious funk, organ bass no less...good luck man.