When the Stoics invoke duty, they have something special in mind. Yes, it involves performing your obligations, but there is more to it. For one thing, the Stoics see duty everywhere — or rather, they see life as a collection of duties, including but not limited to your job.

Duty is rooted in self understanding. What are you able to do well, the Stoics ask? What service is required? Throw yourself into that. Each of us has undeniable talents and abilities, whether they are physical, emotional or intellectual. More controversially, your natural makeup and disposition suggest there are things you should not do — you will never do them well, and they will offer perennial frustration. Hopefully, or ideally, your natural abilities will be cultivated and deployed most effectively and fruitfully. This makes for joy.

In essence, Seneca calls for a change of focus: Instead of straining to discover your one true passion, and devote your life and soul to it, study yourself and the needs of those around you. Frankly assess what you can do, how you are best equipped to serve, and work. Also: identify the several jobs you are called to do — inside and outside the home — and do them well.

Seneca also urges Serenus to avoid pinning his hopes on perceived results; we may not see any. Too often, we throw up our hands in despair when we think our efforts have no impact. Too often, we misjudge the nature and standard of success. But human perception is prone to error, philosophers have long pointed out. We are often ill equipped to measure, much less detect the fruits of our labor. We must, Seneca says, “just act” — just do your duty, and think of little else.

To illustrate, Seneca tells the story of the ill-fated Julius Canus, who was condemned to death by the emperor Caligula. In prison, Canus played a game of draughts while awaiting his execution. When the centurion came to lead him to his doom, “he counted the pieces and said to his companion, ‘Mind you don’t pretend you won after I’m dead,’ then with a nod to the centurion he added ‘You will testify that I was one piece ahead.’ Do you suppose that Canus played a game at that board?”

Life is a game, or a play, the Stoics contend, where we have roles to act out. These are our duties. I, for example, am a professor, sometimes a writer; but also a father, a husband, and son; a colleague, citizen, neighbor and friend. There are certain things I must do in these roles. There are expectations of me and duties to perform beyond my career, as stipulated by my nature and place in society, and they require my attention. And my duties will change with time and age.

Play the role you are given, Seneca urges. Play it seriously, and diligently. But recognize that it is only a role, one among many — and not of your design or choice. When you see your duties as various roles you must play, and your life as a collection of these roles, this will alleviate the urgency and anxiety that burden any given task — including, or especially, your career.