Well, what I do “for living” is eat, sleep, breathe…

So, no, to understand the sentence, it definitely needs the article “a”.

To speak to your point, though, yes, that is very similar to what was discovered by Angela Duckworth in her research for Grit. If people are pursuing a passion, they continue through the yucky parts, because it is so consuming and rewarding to them. It’s not that they start out having perseverance… it that they persevere because they love whatever it is they’re doing so much. And that tends to pay off in the long run with success.