Musicians are artists, performers, and entertainers
Music is art but it's also entertainment. When you perform, you are providing entertainment, albeit of a high quality. See yourself as an entertainer, not only a musician, and your performance will improve greatly.
The reason? Entertainers focus on the needs of their audience; this audience-centric view demands that performers place themselves in the shoes of the public. How much or how little you practiced, whether you broke up with your significant other last week, or are suffering from an upset stomach mean very little to an audience that is giving you the privilege of its time and attention.
By all means practice as diligently as possible to give a near-flawless performance. However, at performance time, stop focusing on minutiae which probably mean little to your audience. Instead, make it your mission to entertain them with your performance. In general, do not practice more than one hour on the day of a performance. At this point, focus less on the technical aspects and more on telling your story through intonation, dynamics and passion! Or, as my former piano teacher, Milton Kaye used to say, “I don’t care how perfect you play…just don’t be boring!”