I've gotten to the point of being able to cover up my mistakes better than I can prevent them.
THIS. High level players are not mistake free: they recover from mistakes with appropriate style and taste.
Nailing the material while distraction free and alone, or in the familiarity of a rehearsal, is easy. But at a gig there are a thousand tiny things that are going sideways at all times, begging to distract you from what was easy in the bedroom or rehearsal space.
Some say "do not practice until you get it right: practice until you can't get it wrong." That's a very high bar in my experience, but a good direction to aim in. What you want is an ingrained level of familiarity both with the material
and the stylistic/ musical context of the piece. So that if you wander off of "correct" you at least fall into the right style / key / arpeggio
When I feel prepared sufficiently It is almost like the song exists in a prefect form outside (inside?) of me. If I can get my mental and physical habits out of the way it comes through effortlessly. Not
perfectly, but in a way that has a kind of natural pull towards a good and proper feel and execution. Like
Twinkle , Twinkle, Little Star, I know exactly how it goes, I can sing it easily and correct quickly if I mess up.
The one practical thing I have done is "naked metronome" practice. Just the bass, maybe a chart, and a metronome. No band, no backing track, and no stopping for mistakes. I try to play the bass line all the way through an
make it sound good with no help. I find it really solidifies my understanding of a piece. The
make it sound good part is important. Not merely playing correctly, but playing something with honest emotional intent behind it. I don't want to understand
how it goes I want to understand
how it feels.
And when I'm onstage and the acoustics are F'ing with me, and the sound guy isn't respecting
my tone , and the smell of the deep fryer is pumping through the fans behind me, and the fire engine is driving by out front, and my ex is sitting at a side table because "we're still friends", simply remembering
how it goes is not enough: what I want to give my attention to is
how the song feels.