We know Stoicism is not simply that lack-of-emotions, stiff-upper-lip thing. Though with a lot of talk about reason and controlling your emotions, it's easy to see where that somewhat modern-day twist originated.
What Stoicism is, through all the varying interpretations, is a blueprint to live a better life. A path to what some call "happiness."
To get there, the ancient Stoics believed in introspection (it's a philosopher thing). They laid out three areas of study that a thoughtful, inward-gazing Stoic should embrace and practice to achieve that happiness or fulfillment.
1) Physics: By this, Stoics meant the study of both the natural universe and of metaphysics (that which is beyond the physical world). The word "nature" is used as all-encompassing; it not only includes nature as we know it, but God and the divine as well. Stoics saw it all as one [sources: How to Be a Stoic, Traditional Stoicism].
Here's how philosopher Massimo Pigliucci puts it in his blog How to Be a Stoic, while pointing out still-hot disagreements on the religious and spiritual notions of Stoicism: "A crucial idea that the Stoics derived from their physics is that life ought to be lived 'according to Nature,' which can then in turn be interpreted as 'in agreement with what Zeus (God) has ordained,' or simply lived according to reason, developing to its best that most specific attribute of the human animal. Being a secular person, I obviously go for the latter interpretation." Stoics believed the universe began in a cosmic fire and will end the same way, but begin again.
2) Logic: This includes the study of psychology and other social sciences (economics, sociology, history, etc.) and is often referred to as "reason," a treasured concept in Stoicism. It is through reason, Stoics believe, that we gain knowledge, and with knowledge we can better understand and flourish in the world around us [source: How to Be a Stoic].
3) Ethics: Stoics believe, above all else, in four great virtues: courage, justice, wisdom and temperance. A Stoic life involves trying to nourish these values, on a daily basis, in order to become a complete person and live a good life.
To live a Stoic life, believers must thoughtfully consider "good" emotions (love, joy) and "bad" ones (jealousy, anger) but not let any of them interfere with their pursuit of virtue. Stoics aim for a state of apatheia — not quite what we know as apathy, but a place without distracting emotions or excitement — in order to think clearly, reason correctly and work toward a virtuous life. Rather than suppressing emotions, these must be transformed to achieve inner calm [source: How to Be a Stoic].