I was one of the lucky ones. I had music teachers very early on, and grew up in the home of a music educator who was a high calibre performer herself. Those music teachers taught me the importance of learning well for public performance, and here are a few of the favorites.
Lesson #1 – Take small bites.
Don’t try to manage too much at once. Assess and accept, and keep working patiently.
Lesson #2 – Get it Right.
Ability is determined in the practice room, if you are willing to stay long enough to only get it right.
Lesson #3 – Be efficient and adaptable.
Yeah, that might count as two, but they are related and worth putting together. If a struggle is encountered, then figure out how to learn it as well and as quickly as possible. Make a game of it, work it into the muscle memory, and eliminate doubt.
Lesson #4 – Trust
Trust in the preparation – and make sure you did enough of it.
Lesson #5 – Don’t sweat the small stuff.
The more amplified the success and failure, the harder life is. Sometimes, for whatever reason, performance can be better or worse than usual. Cool it and keep perspective.
John Wiens, Conductor 
Good lessons, very well put.