We are all equally endowed with willpower but we differ in the power of habits that we have ourselves created and have now to struggle with.  We also differ in terms of the skillpower*  that we bring to the fight with the habitpower.

*skillpower: coping power (which is a reflection of our mastery of such coping strategies as craving control and emotional self-regulation)

related: Weak Willpower or Habitual Automaticity?