Stoicism is an ancient Greek philosophy founded in the early 3rd century BC by Zeno of Citium. This school of philosophy guides us towards a life of tranquility and virtue. Tranquility is a state marked by the absence of negative feelings like anger, sadness, worry, and stress, and the presence of positive feelings – in particular joy. Virtue is the aim for excellence as a human being living in accordance with nature. Believe it or not, it is one of the roots of cognitive behavioral therapy (CBT).