"Better is one's own duty, though devoid of merit, than the duty of another well discharged. He who does his own work does not incur sin."
Modern explanation
When the day pushes against you, remember: The work that fits your nature will tire you in a way that still feeds you. Borrowed work only drains.
Practical application
Do the work even when motivation has left the room. Discipline is borrowed motivation.
Reflection question
What would I do if I knew this work was preparing me for something I can't yet see?