Why does Epictetus say to remind yourself that your child will die?

The point is not to feel less

Epictetus is not telling you to love your child less or to brace for grief by going numb. He is telling you to see your child accurately: as a human being, and therefore as mortal. In the Handbook he gives the instruction as a general method, starting from trivial cases and working up. If you are fond of a ceramic cup, remind yourself it is a ceramic cup, so that if it breaks you are not disturbed (Handbook 3). He then applies the same move to the people you love most: "If you kiss your child, or your wife, say that you only kiss things which are human, and thus you will not be disturbed if either of them dies" (Handbook 3).

In the Discourses he gives the line its sharpest form. He imagines actually saying it, out loud, mid-kiss: "What harm is it while you are kissing your child to say with a lisping voice, To-morrow you will die" (Discourses 3.24). He knows how this sounds. He immediately names the objection himself: people will call it a bad omen, words you should not speak over someone you love. His answer is blunt: he does not care whether it sounds ominous, only whether it is useful (Discourses 3.24).

What the reminder is actually doing

The reminder is not a prediction and not a wish. It is a correction of a false judgment you are prone to make without noticing it: that your child is the kind of thing that will not die, or that is somehow yours to keep. Epictetus's whole method rests on the distinction between what is up to us and what is not. Your opinions, your desires, your own actions are up to you. Other people, including the people you love, are not (Handbook 1). A child is a human being on loan, not a possession you hold by right.

Handbook 11 makes this explicit with a different image. Don't say "I have lost" a child or a wife who has died, Epictetus says, say "I have returned" them, the way a traveler returns something borrowed. "Is your child dead? It is returned" (Handbook 11). Take care of what is given to you, he adds, but do not regard it as your own, the way a traveler at an inn does not treat the room as his house (Handbook 11).

What changes if you take this seriously

If you actually run this exercise, something shifts in how you hold the people you love. You stop loving them as fixtures and start loving them as what they are: fragile, temporary, not under your control, and for exactly that reason worth your full attention now. The reminder is aimed at removing a specific kind of disturbance, the shock and protest that come from having believed something false, not at reducing how much you care. Epictetus is explicit that the goal is not to be hindered, not to lament, not to find fault with gods or men when something not up to you goes the way nature always said it would (Handbook 1).

This is also why the Stoics did not treat death only as a future threat to dread but as a fact to place beside present happiness, the way winter stands behind every fig (Discourses 3.24). The practical version of the exercise is simple. Tonight, when you say goodnight to someone you love, let yourself notice, without flinching away from it, that this will not always be possible. Then give them your full attention anyway.