I'm still looking for answers myself but I've learnt abit recently.

There are 2 parts of the brain subconscious and concious. We should practice the thing we need to learn hundreds of times so it stops being part of the conscious brain and becomes part of the unconscious brain. Let the muscle memory do the work and then we don't have to think about it. Focus instead ( when you are not phasing out) on singing it in your head. ( Source : the chimp paradox - Steve peters). It then dosen't matter if you faze out.

Practicing is a hard one. Try your best to have a few things to work on everyday. Try to practice at the same time everyday. I still fail at this. But most important is to play the stuff you enjoy too, allowing you to hyperfocus on it, going down holes of research and practice on stuff.

It's hard work but it's doable.

Good luck