I was searching for the origin of the quote, and found another version:"...if you were guaranteed that you would succeed." Whatever, it's like asking is the devil or god in the details? (Actually, it's god, the devil quote is a derivation, but widely and more frequently used.)
Which got me to thinking, why must we frame everything we do in terms of success and failure? (Maybe Nike has it right: "Just do it.") I sometimes feel beset in a world seeking growth and improvement, feet held to the fire through processes and procedures, metrics and measurements, profit and loss, time and money. Good and evil, god and the devil. Right and wrong, rights and wronged. As if living was just a matter of applying an algorithm.
I would rather ask "What would you do if success or failure didn't matter, one way or the other?" I think that's the real question. Does a guarantee of a "successful outcome" matter? If not, those are likely the things you might really want to do.
I should go do some goal-less meditation now, but I need to get ready to "go to work," the extra-curricular thing I do to put my way through the lifelong-learning courses I have signed up for. Once I went to school to build a foundation for a career. Now I have a career that feels like something I do to put myself through school.
A word from the older but wiser to my younger readers: find and maintain work that isn't separate from what you love to do. And think about what you would do if you had all the time in the world. (Well, you do, really...it's probably money that holds you back, time and money being too often conflated. And there's the rub.)