Discipline is a habit. But it’s also a choice and not an easy one. Discipline is ignoring what you desire in the moment for what you want in the future.

Some people think discipline is just for #hustlebros who want to wake up early and take cold showers, but it’s more than that.

Discipline is choosing to go back to your hotel room alone when the beautiful person at the bar has been giving you eyes all night after a fight with your spouse.

It’s choosing to let your money quietly compound in index funds while everyone else gets rich from pumping Game Stop. It’s the ability to show up every day for five years while you work on that degree without being “rewarded” for it.

Discipline is everywhere and applicable to everyone. Here are six rules I learned about self-mastery from Discipline is Destiny by Ryan Holiday.

Most of the lessons are pulled from chapter titles, so thanks to Holiday for making that easy. I’m just highlighting the ones I thought were most important.

1. Treat the body rigorously

Lou Gehrig was no "good-time Charlie." He wasn't a drinker and didn't chase thrills or girls. "The obligation of a champion," Holiday writes, "is to act like a champion...while working as hard as somebody with something to prove." It wasn't about his "image" or wanting to be "above reproach." Gehrig knew his body was a machine, and it was how he made his money. He wasn't going to abuse it, and neither should we.

Someone would write about him that he didn't drink, "not because of any prissy notions of righteousness that it was evil or wrong to take a drink but because he had a driving, non-stop ambition to become a great and successful ball player. Anything that interfered with that ambition was poison to him." Muhammad Ali would say later, "When a man can control his life, his physical needs, his lower self, he elevates himself."

Musonius Rufus, speaking on a similar note, writes, "Obviously the philosopher's mind should be well prepared for physical activity, because often the virtues make use of this as a necessary instrument for the affairs of life. We use the training common to both when we discipline ourselves to cold, heat, thirst, hunger, meager rations, hard beds, avoidance of the pleasures and patience under suffering. For by these things...the body is strengthened and becomes capable of enduring hardships, study and ready for any task."

You train your body and mind in moments you can control, so you can control your body and mind in moments you don't.

2. Don’t let anything have mastery over you

One day in 1949, Richard Feynman felt an increased craving for a drop of alcohol, separate from the reward of celebrating the results of hard work. Right then and there, he gave up drinking. Because as Holiday writes, "Nothing, he felt, should have that kind of power over him."

A core idea of self-discipline is to be extremely wary of anything that controls you. These can be vices like caffeine, alcohol, or drugs. But they can also be virtues like success or working out. The desire isn't the issue. It's the need.

3. Show up every day

Thomas Edison said, "The genius hung around his laboratory day and night. If anything happens, he's there to catch it; if he wasn't, it might happen just the same, only it would never be his." Showing up when it's easy...is easy. But doing it when it's hard is when it really counts. Those are the days when greatness is born.

John Steinbeck called these "dawdly days." Holiday explains, "Those days when everything seems out of whack, when you're just not feeling it, when the distractions won't stop." Showing up on those days "is the first step to greatness."

4. Sweat the small stuff

No big project has succeeded by ignoring the small stuff. "It is the loose ends," Zelda Fitzgerald said, "with which men hang themselves." There's an old saying about a horse, for want of a nail, the kingdom was lost. For want of a nail, the shoe was lost. And then, because of the shoe, the horse was lost. Because of the horse, the rider was lost, and because of the rider, the message, and because of the message, the battle, and because of the battle, the kingdom...

For want of a nail, the kingdom was lost.

5. Keep the main thing the main thing

Anyone who has not groomed his life in general towards some definite end cannot possibly arrange his individual actions properly. -- Michel de Montaigne.

Holiday writes, "If you don't know where you're sailing, the Stoics said, no wind is favorable." He continued, "the secret to success in almost all fields is large, uninterrupted blocks of focused time." To do this, we can borrow a line from E.B. White, who replied after being asked to be a part of some commission, "I must decline for secret reasons."

It sounds simple, but doing it isn't easy. To keep the main thing the main thing requires you not to be a slave to your ego. After you become successful, they want you to appear on every podcast, go to every conference to "network," and be a part of communities so people know who you are. Your ambition and ego will want you to continue walking down the path of success and fame, but that ambition isn't helpful if it's not taking you anywhere. You must learn to tame ambition and to keep the main thing the main thing.

6. Expect much from yourself, little from others

This is an important one.

You have to be disciplined. You don't have to force discipline on others. Those people are just annoying, and no one likes them. Don't judge other people for drinking if you don't. Don't make someone feel bad for not running, reading, or waking up early.

Their life is not in your control, so don't act like it is. Hold yourself to high standards.

Cato the Elder said, "I am prepared to forgive everybody's mistakes except my own." Ben Franklin said something similar: "Search others for their virtues, thyself for thy vices." Holiday writes, "Be a strong, inspiring example and let that be enough." He also shares a story from one of Lincoln's secretaries who would marvel at her boss "never asked perfection of anyone, he did not even insist, for others, upon the high standards he set for himself."

On a similar note, Seneca writes, "Happy is the man who can make others better, not merely when he is in their company, but even when he is in their thoughts." So though you shouldn't hold people to your high standards, you should inspire them to be better just by being you. Not giving some fake speech or showing off your accomplishments, but by your character, your attitude, and your approach to life. Holiday writes, "The fire within us can burn bright enough to warm others. The light within us can illuminate the path for others."