How to Do What You Love by Paul Graham:
Another test you can use is: always produce. For example, if you have a day job you don’t take seriously because you plan to be a novelist, are you producing? Are you writing pages of fiction, however bad? As long as you’re producing, you’ll know you’re not merely using the hazy vision of the grand novel you plan to write one day as an opiate. The view of it will be obstructed by the all too palpably flawed one you’re actually writing.
“Always produce” is also a heuristic for finding the work you love. If you subject yourself to that constraint, it will automatically push you away from things you think you’re supposed to work on, toward things you actually like. “Always produce” will discover your life’s work the way water, with the aid of gravity, finds the hole in your roof.