Besides sleep, the other two main variables in your lifestyle that can deeply affect your willpower and energy levels are food and physical movement. Eating well and exercising regularly are daily disciplines that make other disciplines easier. Yes, they do require willpower, but they also strengthen your willpower.
The food disciplines I follow are eating once a day (intermittent fasting), zero alcohol, zero caffeine, and a vegetarian diet rich in fruits, plants, grains, and nuts. For exercise, I do a mixture of Kung Fu and Yoga. This work for me.
Having said that, these are not areas of expertise for me, so if you want to learn more you should look for specialized advice from experts in these topics. Here you will find just some pointers.
One of the key elements of diet, for the sake of cultivating willpower and self-discipline, is maintaining a stable level of blood glucose. This is done by eating food with a low glycemic index (the what you eat approach), or through intermittent fasting (the when you eat approach).
The glycemic index (GI) of a food item tells you how quickly that food is broken down into glucose, which then replenishes your system. The lower the GI, the more gradual the breakdown process—meaning that there are no big spikes followed by rapid falls. With that, your energy and willpower become more stable and reliable.
Intermittent fasting is time-restricted eating. You get all your daily food intake in a small window of time and do a water-only fast for the rest of the day. The most common protocol is the 16:8, where you eat during an eight-hour window (e.g., from noon to 8pm) and fast for the other sixteen hours. Another common protocol is the 20:4, also known as OMAD (one meal a day). Intermittent fasting stabilizes your blood sugar levels since you are no longer getting spikes and falls every three hours.
What is the importance of physical exercise for self-discipline?
It trains your willpower. It reduces fatigue, thus improving self-control. Exercise also increases the supply of oxygen and glucose to the brain and is known to increase the volume of the prefrontal cortex (the part of the brain responsible for self-discipline). Research shows that just a few months of regular exercise can significantly improve your self-control and willpower—and that this translates to positive changes in emotional control and financial decisions as well.
Kelly McGonigal, PhD, in her book The Willpower Instinct, explains that regular exercise reduces temptation, relieves stress, and is a powerful antidepressant. Physical exercise—like meditation—makes your brain bigger and faster; it supports heart health, and it improves sleep.
Eating a healthy diet and exercising regularly will not automatically make you a master of self-discipline, but these habits will improve your willpower baseline and thus multiply the fruits of your efforts.