Jealousy can be a very constructive emotion.

I’m not talking about the kind that comes when your husband’s ex shows up as his Facebook friend. No, I’m talking about the feeling that comes when you covet not what someone else has, but what someone else does.

Case in point: Tomorrow my baby brother graduates with a PhD. This is something that I long wanted, especially when I was a starry-eyed English major, wishing I could just read and discuss great literature all day every day with smart people. But at 21, instead of grad school, I earned my first M.R.S. degree, and that was that. So how do I feel now that the first doctor in the family is not me? Great. I’m serious. I’m so proud of my brother I could bust a gut. He worked so hard and so long for this. Children have been born and loved ones have died as he pursued this degree. His students are lucky to have him as a prof.

Second case in point: One of the reporters I used to work with at an itty bitty newspaper in Arizona just won the Pulitzer Prize. The Pultizer! I used to ache for that. When I was a reporter, all I wanted was to work for the Wall Street Journal or the New York Times someday and win the most prestigious award in my field. So how does it feel now that someone I used to work with has captured the prize? Again, great. I’m very happy for Paul Giblin and I hope this leads him to the Journal or the Times.

Am I now such an enlightened being that I am immune from jealousy? Shit no.

As recently as last winter I thought I had everything I ever wanted. Then I learned that a friend from an old writing workshop had her novel published. By a major publisher. And it’s been nominated for the Orange Prize, which is the U.K. equivalent of the Pulitzer. This was the novel she was working on in the workshop. Where’s mine? In my desk drawer. How do I feel? Like I want to eat my own liver. With a spoon.

So, here’s why I think jealousy is a constructive emotion. I believe it’s the most honest indicator of the heart’s desire. The most uncorrupted, the most base. But as useful as it is, it cuts deep. Longing unfulfilled makes the heart sick. So when you feel overwhelming jealousy, and it points you somewhere, you’d better go. Who knows — jealousy could be the true voice of God.