Who said "Motivation comes from vithin; no one can give it to you."?

This quote is attributed to Chekov.

Motivation comes from vithin; no one can give it to you. - Chekov

"Motivation comes from vithin; no one can give it to you."

Chekov Motivation

"In Russia, ve have a saying: 'The best time to plant a tree vas twenty years ago. The second best time is now.'"

"Vhat is science vithout the courage to explore the unknown?"

"I have alvays found that friendship requires vork, but it is vork vorth doing."

"The human spirit is remarkably resilient - ve survive vhat ve must endure."

"I believe in working hard for what you want."

"Never underestimate the power of determination."

"I don't need a reason to fight."

"The most important thing is the mission. Nothing else matters."