Let me give you some musical advice. Make mistakes. Not on purpose of course, but don’t spend your time worrying about them. I used to, and that itself was the biggest mistake I could have made. Because listen, as long as you are good and you know your stuff, mistakes don’t matter. (Caveat: mistakes matter to some, but not to those who matter)
But let me be clear about what I consider a mistake. Showing up to a rehearsal not knowing your music may be a mistake, but those wrong notes you sing are not. Those are calculated decisions made earlier when you decided to do something other than learn your part. When I say mistakes, I am referring to the literal mis-take. This particular take had an error. For whatever reason, you sang a wrong note, despite having gotten it correctly the seven other times you just ran through the piece. That is a mistake. One that will probably not be repeated. And if you let yourself get hung up about it, you could have further problems. So relax.
Recently I had the chance to listen to two different people sing the same piece of music. One of them sang all of the right notes in a passable manner, though the voice and artistry was a bit lacking. The second one sang with beauty, phrasing, intent, and mastery. Except towards the end, this person came in on a completely wrong at a big entrance. It took this singer about a measure and half to recover, and the piece was finished with style and confidence. I will tell you right now. I would rather listen to the second version any day of the week, mistake and all. The choice between a beautifully sung line with a clunker in the middle of it and an averagely sung line with no clunkers is very easy for to me make. Give me the mistake.
We all make mistakes. This is because we happen to be human beings, blessed with a concrete longing for, and absolute inability to achieve, perfection. But honestly, screw perfection. If you want perfection, go listen to someone who has been autotuned. Or a robot. Robot concerts will be very big next century. But in this century, continue to to strive for perfection, knowing that you will never reach it. And just be good. Work hard, get better, be proud, and don’t ever worry about the mistakes. The only reason to worry is if you play it so safe that you stop making them.