If you go to dictionary.com and look up muse,  you'll find that the term muse originates from Greek Mythology.  Zeus had nine daughters who presided over the various arts and sciences such as poetry, music, dance, astronomy, etc.  In another definition, a muse is "the goddess or power regarded as inspiring a poet, artist, thinker, or the like."
I was talking to a friend about my Pizza Blog and the New York Pizza Finder web site when he asked me, "Have you read the Four Hour Work Week?  I said, "Yes," and he asked, "So the pizza blog is your muse?"
It was kind of strange because I had not thought about this previously, but I guess it's true.  I started blogging about New York Style Pizza over two years ago, because I am passionate about New York Style Pizza, I think it should be everywhere, and sometimes it's quite hard to find.   The result is that I've become a part of a small community of people who share my passion.  If you read the comments on the site, you will quickly realize that there are many people in the same boat I was in-- ex-New Yorkers or New Jerseyites who are now living elsewhere, who can't find a decent slice of pie, or who finally did find a good slice and want to tell the world about it. 
Here's to doing what you're passionate about! 
Tom S