A stoic quote by Epictetus from Discourses II, 21.20
You say the speculative topics are useless. Useless to whom? Only to people who don’t use them as they should. I mean, salves and ointments are not useless to people who apply them when and how they’re supposed to; weights are not useless in themselves, they’re useful to some people, worthless to others.
― Epictetus Discourses II, 21.20