Do You Want to Increase Your Willpower?
The basic definition of willpower (also called self-control, self-discipline, and self-regulation) is the ability to control oneself in regards to ones emotions, desires, and actions. Recently there's been a wealth of research on willpower, and the evidence shows that in many ways, willpower works like the muscles in your body do. Each of us has a certain amount of willpower per day. It is a limited quantity that fluctuates from person to person.
For some people, willpower is freshest at the beginning of each day (early birds), while others feel that their willpower switches on later in the day, with it peaking in the evening hours (night owls). What is consistent in either case is that, just like your muscles, your willpower tires out as you use it.
Willpower can also be strengthened over time by practicing it, just like a muscle. For example: Turning down the donuts at your work's morning meetings may temporarily drain your self-control, but over time your resolve will strengthen, making it easier to turn down future temptations. This is how self-discipline is developed. You can replenish your willpower after a restful night of sleep, after a good nap, and by taking breaks to meditate, go for a short walk, or by doing some breathing exercises. That's why it is harder to stick to eating and exercise plans after a stressful day.
What drains willpower?
Your levels of self-control and self-restraint can be diminished by more than tempting foods. That same willpower muscle can be drained by many things including a poor night's sleep, controlling your temper (to suppress emotions), forcing yourself to laugh at an unfunny joke (to express false emotions), sitting through tedious work meetings (practicing patience), pushing yourself to keep working when you are tired. These examples deplete your self-control if you let them, but practicing them in the right amounts will strengthen your willpower over time. The successfully-minded person is aware of these brain-drains, and it's the awareness that allows for contingency plans.
You can't help getting drained as your day progresses, but you can take steps to stay on track, such as having a commitment to a buddy or trainer so you don't miss your workout, or having meals pre-planned so you eat healthy.