In yet another foray in to describing the two types of effort needed to master music the most quickly, consider a car race. There are 2 people involved, a car, and the race. The race is being a good and great musician. The car is the song, the exercise, your entire musical effort. When you rehearse you need to be two people, two people in a race. Part of your time (2/3rds) you are the mechanic. You pull the car apart, you work on the transmission, you tinker with the carburetor to get a better response, you polish and fiddle and tweak to get that car the very best it can be. But suddenly the race car driver comes up (he’s you) and he says, “Well, that’s great, but we’ve got a race to run, so you’ve got to put this baby back together so I can drive it”. And then you, as the driver, get in that car and get it on the track, and whatever happens, you’ve got to make the best of it to do your best to win that race. That’s 1/3 of your practice time. The part of your time as the mechanic is when you, whether on a song or an exercise, repeat and become mister nit-picky to get it absolutely perfect. And you as the driver is the part of your time where you perform the song straight through no matter what happens.
Read ahead, keep your eyes a measure ahead of where you play. Don't just stare where you're playing, it's just a crutch. Makes U 2x as good.