No, it's not "Grease."
Lots of words spring to mind: perseverance, technology, stubbornness, knowledge.
I think my word would be: "payoff". You're not going to get rich. You'll barely make minimum wage if you consider all the hours you put into it. When you think of the cost of conferences, promotion, travel ... well, it boggles the mind.
Your payoff is what YOU get out of it. Are you writing to make a point? Do you have a story that's struggling to get out? Are you tickled pink when someone stops you and says, "I just discovered your books and I've bought every one"? Do you love the 5-star reviews? Are you amazed someone is paying you to do this?
PAYOFF. There is one. Even if you don't get published, there's a payoff. It might be a sense of satisfaction at a job well done. It might be a contest win. It might be knowledge gained.
Figure out what your PAYOFF is and the writing will take care of itself.