What do you like doing?
What are you great at?
What does the world need?
What are you paid to do?
And where do those things coincide?
For me, it's teaching. Teaching a subject that I am passionate about. Watching the small transformations on people's faces when they suddenly realize a truth about how they work. These things get me out of bed in the morning.
Teaching is also a vocation I fought against for years. Both of my parents were teachers. So I went to school for acting. I got a masters degree. I run a company. And, I teach. When I sit down and think about all the things I do, the one that brings me the most joy is teaching.
So ask yourself - where do those questions coincide for you? And how does that answer change your views on what you do?