In our current culture of celebrity worship, we often look to well-known names and faces to teach us things. You'll find enough lessons inadvertently taught by the likes of Elon Musk and the late Steve Jobs to fill a library full of books.

But, we can also learn from people of the distant past. Take Roman emperor Marcus Aurelius (121-180 AD), for example. Devoted to the ancient Greek philosophy of Stoicism, Aurelius was known as the "philosopher king."

To keep himself true to Stoicism, Aurelius wrote a book that was never meant to be read by the public, but was posthumously published as the Meditations, chronicling 12 different periods of his life.

And now, allow me to generalize and oversimplify five of these important lessons so we can apply them to the 21st century.

The longest-lived and the shortest-lived man, when they come to die, lose one and the same thing. (Book 2, Ch. 11)

Life is brief. We came from atoms and we will go back to atoms in the infinite universe, so be genuinely happy and enjoy the opportunity to have your human experience.

Don't be afraid to take risks because it is the journey of life rather than the destination that counts. The real value in life is in the experiences you have, not what you end up with at the end.

Never esteem anything as of advantage to you that will make you break your word or lose your self-respect. (Book 3, Ch. 7)

Be truthful to others and yourself. As leaders, trustworthiness and respect form the ground you stand on. Without them, you will not be able to operate as a true leader.

If you find yourself taking an action just because you can benefit from it, ask yourself if it means breaking your word and also ask yourself if you had to explain your decision to take that action to someone you care about, would you feel ashamed while doing it? If the answer is "yes" to either of those questions, maybe that action isn't worth taking.

Remember that all is opinion. (Book 2, Ch. 15)

Everything we read and hear is an opinion, not a fact. Everything we see is a perspective, not the truth.

Expect to be wrong from time to time and expect to be given wrong information occasionally. Leaders often don't deal with absolute facts, which means you have to ask a lot of questions to get the most accurate information. If you are making decisions without asking questions, you are setting yourself up for a fall.

Very little is needed to make a happy life. (Book 7, Ch. 67)

There is a longer quote in Meditations (the Gregory Hays translation) that can be added to this point: "Do not indulge in dreams of having what you have not, but reckon up the chief of the blessings you do possess, and then thankfully remember how you would crave for them if they were not yours."

When you only need a little to be happy, it frees you to be a courageous and generous leader because you won't be as concerned with trying to accumulate wealth for yourself. The best part of the Stoic philosophy is the simplicity of its message of focusing your mind on the things you have versus what you do not have and living the life you do have versus pining for a life you don't have.

Aurelius's book is full of gems for both current and aspiring leaders. And it's refreshing to see that even though Aurelius was an absolute leader with the absolute power that so many modern day tyrants crave, he was content and refrained from abusing that power. (Although, whether or not he abused his power would, of course, depend on your perspective.)