If we only relied upon motivation to drive us to do things we wouldn't get much done at all.  Motivation is fickle and unreliable.  Instead we must rely upon discipline to drive our actions to fuel our success.  Discipline is independent of motivation and energy, but instead relies upon passion and commitment to achieve what it is we desire. 

Discipline is choosing between what you want now and what you want most.  Abrahm Lincoln

All successes beging with self-discipline.  It starts with you.  Dwayne Johnson

Self-discipline will get you farther than motivation ever will.  Anonymous