Dancers are artists that strive for perfection.
Perfection is the impossible standard for ballet.
No one can ever do a variation, step, or combination perfectly, without some mistake.
But that is what makes dance art. Art is something that strives to reach perfection and create emotion, yet it can never reach that highest point of perfection.
There is always room for improvement in ballet, and always room to mess up, but there is always, always a once in a lifetime opportunity to dance on the brink of perfection.