Here are some potentially new and useful ways of thinking about your best.
I use two different ideas about my "best" so I can constructively measure both what I want, and where I truly am in relation to what I want. Then I make my choices depending on what will close the quality gap between these two types of "best".
Your Two "Bests"
Absolute Best - what you can do.
True Best - what you actually do.
Absolute Best is an ideal. My constant goal is to shoot for this absolute best. I learn about and protect this ideal goal, and my belief that I can reach it, with all my might. ...and with all my good sleep habits, and eating, and thinking, and and and...
I believe when I prepare as well as possible, I can do my absolute best. My absolute best is always what I want to do. I work with as high quantity and quality of work as I can, so I can bring as much of this 'ideal best' to my preparation and performance.
Now, the reality is that no one is perfect. I often could sleep more, and eat better, and choose better thoughts, and read more, practice more, practice better, and and and... So that leaves me with:
True Best - reality. Basically I am always doing my True Best, because it is what I actually just did. Sometimes my True Best gets me hired. Sometimes my True Best isn't very good, because maybe I worked too hard the night before, or I forgot to stay hydrated or my flight was delayed. Maybe right before the note I missed, I thought about who was in the audience or what I could win if I played this note impressively.
I use Absolute Best as the example of the ideal version of what I'm working on. It's what I could do if I trained perfectly. It is what I aim for! But since I can't train perfectly, it still remains my measuring stick against which I compare, as constructively as possible, my True Best.
Whatever the reasons are for each quality gap between my Absolute and True Best, calling what I just did my True Best helps me embrace what I just did. It's a humbling thought to believe that everyone is always doing their best, but it helps me resist judging anyone (especially myself!) too harshly. A better way I've found to say this is:
Everyone is always doing their true best.
This is not a cop-out way of lowering your standards. Don't think, "I did my best, so I'll just keep doing that." Far from it! Keep your eyes constantly on the greatest Absolute Best you can! Obsess about that. Refine how good you can imagine it being, and relentlessly work toward and shoot for that.
This week's goal - Know your best.
Perform, and then look at what you just did, your True Best, and think about what you can do better for next time. 99.9% of the time, nothing "happened" to you. You just did your True Best with everything that led up to that moment...to that performance. Accept it, and learn from it.
When you look at your performance you just gave with an accepting truth approach, find a way to objectively say, "Ok, that was my True Best." ('cause it really was!) Set your goals even more aggressively on a new Absolute Best for next time that includes more research, better practice habits, and even a healthier lifestyle. Go after your new Absolute Best with EVERYTHING you got this week! See where your knowing your best takes you.
...and remember, you can't train 24 hours a day, 7 days a week. You have to rest, eat, and laugh a bit as well. Live a life around your work, and bring those story-aspects to your performance too. Manage all aspects of your life that pertain to your performance excellence. Knowing what that Absolute Best is for you will help guide your choices this week. Seeing what you do along the way as a constant True Best will help you see where you truly are, and help you make optimal choices for each next step toward your Absolute Best.