Desire

From the book The Best of Success, compiled by Wynn Davis:

Desire -  Desire alone is not enough. But to lack desire, means to lack a key ingredient to success. Many a talented individual failed because they lacked desire. Many victories have been snatched by the underdog because they wanted it more. So if you desire -- intensely -- and you act upon it, then everything stands within your reach.

"The starting point of all achievement is desire. Keep this constantly in mind. Weak desires bring weak results, just as a small amount of fire makes a small amount of heat."
   -  Napolean Hill

"Nothing stops the man who desires to achieve. Every obstacle is simply a course to develop his achievement muscle. It's a strengthening of his powers of accomplishment."
   -  Eric Butterworth

"You learn that, whatever you are doing in life, obstacles don't matter very much. Pain or other circumstances can be there, but if you want to do a job bad enough, you'll find a way to get it done."
   -  Jack Youngblood