If you are distressed by anything external, the pain is not due to the thing itself, but to your estimate of it; and this you have the power to revoke at any moment.

Marcus Aurelius (121–180 CE) was a Roman emperor and Stoic philosopher known for his posthumously titled work, Meditations. Assumed to have been written for his own self-improvement, the book examines life experiences through the lens of Stoic principles, which emphasize living virtuously, rationally, simply, and with full responsibility for one’s actions and obligations.