For most of us, the classic ...

For most of us, the classic test of willpower is resisting temptation, whether the temptress is a doughnut, a cigarette, a clearance sale, or a one-night stand. When people say, "I have no willpower," what they usually mean is, "I have trouble saying no when my mouth, stomach, heart, or (fill in your anatomical part) wants to say yes.
 Kelly McGonigal

Quotes from the same author

Go after what it is that creates meaning in your life and then trust yourself to handle the stress that follows.
 Kelly McGonigal
Self-compassion - being supportive and kind to yourself, especially in the face of stress and failure - is associated with more motivation and better self-control.
 Kelly McGonigal