People often ask me where I got my inspiration for one thing or another. Or what possessed me to do something. Or why I have a passion for a particular project. The assumption behind those questions, I think, is that if one could find out where such causes originate, it would be possible to pick a promising field of endeavor then activate the inspiration to spark higher levels of achievement.
But it doesn't work that way. In my experience, I do the project I can't stop myself from doing. Passion is the thing you can't control, by definition. It's the same with inspiration. At any given time there are dozens of projects that I think make sense, but sooner or later one bubbles to the top on its own, logic ignored, and takes over my schedule.
Dilbert was like that. It drove me; I didn't drive it. It felt as if some invisible hand was pushing me. You can label it passion or inspiration if you want. Religious folks might have a different interpretation. The only point is that it controls the person, not vice versa.
If there is a logical component to chasing these passions - beyond the thin rationalizations I tend to layer on them - it is the fact that sometimes you have to get them out of your system to free yourself for the next one. For me, this was most true with my book God's Debris. It was my first non-Dilbert book, at a time that writing such a thing seemed like a really bad idea to all observers. But I had no choice. The book sprang fully formed into my head one day while I was showering, and I couldn't do anything else until I got it out. That meant writing it.
So when people ask how they can find their passion, the answer is that your passion finds you, as long as you can free up your schedule from the "must dos" enough to let it in. When I had a full-time job, before Dilbert, I awoke at 4 AM, sat alone in a comfortable chair with a cup of coffee, and waited. I did that for a year or two, just emptying my mind and freeing my imagination. I don't remember the day I picked up a pencil and started drawing instead of sitting during those hours, but I'm sure I didn't have a choice.