Students (and their parents) should understand the distinction between excellence and perfection.
Perfection is flawless achievement of the ideal. None of us mortal types is going to achieve true perfection in any area of life, except perhaps in the rarest of cases, by some modified definition of perfection. But we can aspire and work toward perfection with near-perfect consistency, and that's excellence.
People who don't grasp this distinction aspire to perfection, but mistakingly (and one might say naively, or even arrogantly) believe they are supposed to achieve it. When they achieve anything less, they see only a failure. They do not value incremental improvement. Moving from a C to a B is not a victory for them. It's still a failure; the intrinsic improvement deserves no affirmation. At its root, this mindset is driven by fear and insecurity—it manifests in anxiety.
People who understand the distinction, on the other hand, know that excellence is the relentless pursuit of the ideal through genuinely optimal effort. They know that's possible every day. They have the humility to value incremental improvements. Victory lies in steady progress. When they come up short of perfection, they are not surprised, and they are not disheartened. Moving from a C to a B is a victory. Not the end of effort, no, but a victory to be affirmed. This is a goal-driven mindset, and it comes hand-in-hand with the healthy kind of stress.
And it isn't just about ourselves. Having this mindset helps us live in accord with others. Because they're just as imperfect as we are. We can appreciate, validate, and affirm their efforts if we aren't first caught up in lamenting their flaws.
Excellence is virtuous. It's about the long game. It's habituated, near-perfect effort, blended with the humility of knowing that perfection is always just out of reach. It's knowing all along that we can't and won't be perfect, but trying to be anyway, because it's the right thing to do. In other words, it's getting over ourselves: acknowledging our flaws (and those of others), and then getting back to work, grateful for the time we have to do it.