Crazies

As I was driving home from the grocery store, I realized that, not only was my main character falling for the wrong guy, I've been feeling more sympathetic towards him as well.  Is this what using first person POV does to a writer?  

So I'm driving down my street, scowling and muttering to myself, questioning my character development, when I notice my neighbor waving to me with a strange expression on his face.  I lost the scowl and waved, but he still looked confused.   

This is not the first time I've done something like this.  About five years ago, one of my neighbors (a lovely neighbor who has since moved) stopped me as I was driving by her house and asked if she'd done something to offend me.  I told her she hadn't and asked why she'd think she had.  She mentioned the scowling.  Thank goodness she said something!  I told her I'd been thinking about something else, and that was the end of it.  But how many people would actually approach me about it?  I've tried not thinking about novels while I'm driving, but my mind tends to work on them whenever it isn't working on something else.

I had another friend ask me yesterday if everything was okay.  She said I'd been looking very serious lately.  She's a very polite friend ;)

So the problem is, what do I say?  I know I can't go around talking about voices in my head; I'd just as soon not mention the writing at all, but it comes up because I think about it so often. Do any of the writers reading this have a trick for turning off your story while you're out in public?