I read Marcus Aurelius' Meditations earlier this year and it had a profound impact on me. It is a book about philosophy and a way-of-life that I can personally relate to. My main takeaways are:

You're not special. We all turn to dust in the end.
We are all connected. From the lowly ant to the celestial stars, we are all working within a system.
Moderation is key. This is true for food, drink, talk, and emotion.
Death is final. Take advantage of what you have now and live each moment.
Listen

The overall philosophy is called stoicism and originated from the Greeks and popularized by Marcus Aurelius. My brother-in-law asked me why this didn't take off like a religion and the truth is that many parts of it did live on in Christianity. They were able to take the best parts of stoicism and made it their own. Additionally, no one likes hearing that they're not special or that there's nothing after this world and religion was able to fill those gaps. Regardless of what you believe in, it is important to live a virtuous life and be true to those around you. I am constantly trying to improve myself and challenge what my perception of the world is.