You want your kid to strive for perfection in everything. So, when he/she does things, you encourage him by saying he can do it even better the next time, and someday it will be perfect.
No, it won't, because being perfect is an unreachable goal. In the meantime, the message your kid receives is:
What I did isn't good enough, therefore I'm not good enough, and until I'm perfect, I won't be good enough.
This mind-set can lead to a lifetime of:
* Apathy and underachievement -- "What's the use of trying?" -- or
* Struggle and intensity -- "Got to keep trying, no matter what."
Well, if you forget the standard of perfection, how do you get your kid to move? By encouraging him appropriately. Do these things: