5 Epic Leaders Who Studied Stoicism -- and Why You Should Too Last week the world celebrated International Stoic Week, and you might be surprised by how many entrepreneurs are understudies of this ancient philosophy.

You may hear the word stoic and, like many, have a misconception that stoics are stone-faced, unfeeling Shakespearean actors on a stage. Not the case.

Stoicism isn't a definition -- it's a practice. And while at its surface it may invoke the idea that whatever life throws at you, you should "grin and bear it," but in practice it boils down to a much simpler idea: Learn to want the things you have and to enjoy life as it is right now. There are many greats that have learned to practice this simple mindset and have enjoyed rich, rewarding lives.

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Here are five epic people who are fans of stoicism that may surprise you.

1. Ryan Holiday

Okay, if you've read Ryan's latest book, The Obstacle is the Way, you may not be surprised that he's stoked on stoicism. Ryan explained to me that by 21, he was the director of marketing for American Apparel. He also trained under the writer Robert Greene, author of the massively successful 48 Laws of Power, and built his own marketing company, Brass Check, which has clients like Google and Tony Robbins.

So where does stoicism come into play? Ryan had a chance meeting with Dr. Drew as a teenager that he says, "changed my life, and I have been studying and writing about it ever since." Considering Ryan's epic entrepreneurial success and the widespread love of his book on stoicism, The Obstacle is the Way -- which has been translated in 17 languages and sold over 100,000 copies -- stoicism just may be the way.

2. Tim Ferriss

Did you know Tim studies stoicism? Neither did I, until I came across this video. In it, Tim goes a little deeper into the basic tenants of this philosophy, including the practice of negative visualization. That doesn't sound good… but it actually is. The idea is that instead of defining your goals, try defining your fears. By visualizing your worst fears you can actually get yourself out of the quagmire of fear and moving forward in action. Watch and learn.

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3. Vice Admiral James B. Stockdale

You may not know about Vice Admiral Stockdale, but you should. Stockdale was a naval aviator during the Vietnam War, when he was shot down and held as a prisoner of war in the infamous Hanoi "Hilton" prison for seven and a half years. I'm going to write that again so you really let that amount of time sink in: seven and a half years.

Pause just for a moment and think about where you were in May 2008, and once you have a good mental picture of that place, imagine you're still there now being tortured. You probably can't -- but if you want to fathom that for a moment, you may have a deeper respect for the impact that stoicism can have in your life. Stockdale says stoicism was how he was able to survive, physically and mentally, and was able to come out of the experience without bitterness. If you can find a more intense example of stoicism in action, I'd love to hear it. You can read his whole detailed account to get a better understanding of what he went through and how he credits stoicism with survival.

4. Pete Carroll

Legendarily positive Seattle Seahawks coach Pete Carroll is an understudy of stoicism, too. His coaching tactics throughout his career have been based on discovering the inner grit of himself, and his players, and on taking the perceived bad things that have happened and transforming them into becoming better. A reader of Ryan's book on stoicism, The Obstacle is the Way, Carroll took the Super Bowl XLIX defeat and onslaught of abuse about his final call costing the Seahawks the game and pushed forward into a new year. That's what stoics do.

5. President Theodore Roosevelt

If you don't know a lot about President "Teddy" Roosevelt, he can be summed up pretty simply. He was a total bad ass. Not only was he our first Roosevelt President, he was an adventurer by nature and a studier of stoicism. Before he was President, Roosevelt was a Rough Rider, journeyed into South America exploring one of the most dangerous and never-before explored tributaries of the Amazon called the River of Doubt, and later as President, he was responsible for setting aside much of today's National Park Land.

What do you imagine he was reading while having all these incredible experiences? Why, the stoics of course. He was known to have carried and made notes in his own copy of the stoicism book, The Discourses of Epictetus with the Encheiridion.

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