Out of Spell Slots

Spoon Theory with a geeky TTRPG twist.

For some people, managing their energy levels throughout the day isn't a consideration. But for others, the amount of energy it takes to get through day-to-day activities is a limited resource. The most widespread explanation of this is 'Spoon Theory' created by Christine Miserandino. And there's a (sort of) equivalent metaphor in most RPG settings: Spell slots. 

Remember: The most powerful agents of magic and artifice are limited by how much power they can expend in a day. Respect those limitations, and remember to take care of yourself.