I'm looking for a word that means "to push yourself". Endurance sort of fits, except that it means enduring a situation where one can't change things. I'm looking for someone pushing themselves when they have a choice to stop or back out.
(In case you're wondering- I want it for the caption of a motivational poster)
ETA: I'm looking for a word that would fit more in the context of "to push yourself to continue when you're bored with what you're doing" rather than "to push yourself when things are physically / mentally challenging".