Tao Te Ching: Chapter 45
Who thinks his great achievements poor
Shall find his vigour long endure.
Of greatest fulness, deemed a void,
Exhaustion ne'er shall stem the tide.
Do thou what's straight still crooked deem;
Thy greatest art still stupid seem,
And eloquence a stammering scream.
Constant action overcomes cold; being still overcomes heat. Purity and stillness give the correct law to all under heaven.