Stumbling upon HBO’s “Six by Sondheim” , I heard this and was entranced:

I learned the only reason to write is for love. Failure taught me you write out of passion. ~Stephen Sondheim

Searching the net I found more here in this article.  Quoting from it:

Sondheim said he also learned an important lesson from his biggest failure, the 1965 musical “Do I Hear a Waltz?”

“We did it out of expediency and to make money,” Sondheim said. “It was easy to write but had no passion and no blood. There was no reason for it to be. I learned the only reason to write is for love. Failure taught me you write out of passion.”

Reflecting on this:

What motivates you?

Where is your passion?