I think, though, that the analysis could use a bit more nuance -- because people will employ the word "jealousy" when they are really talking about something else, one of the other, closely related feelings which may not be as corrosive (or not corrosive in the same way) as jealousy itself. In this post, I plan to differentiate between envy, jealousy and regret, with a brief nod to admiration.
What we are talking about is the emotional reaction a creative person experiences when she observes achievement in others. I do wonder whether it's really possible to discipline ourselves to have the reaction we think we ought to have, which is what a lot of people seem to recommend. But I also think that the different reactions are so close to each other that it may be possible, by a change of focus or a deliberate foregrounding, to cultivate the feeling that is most helpful to you.
Admiration, of course, is the emotion to which we all give lip service, and the one we wish we had all the time. And it's an easy one, when the work is good. When I read a badass short story or a stratospheric novel, I'm so slack-jawed that I don't have room for another emotion. Mostly I just tell lots of people about that story. Sometimes I'll e-mail the author and tell her how much I liked it, and why. I've made quite a few friends that way.
Envy is what I think a lot of people actually mean when they say that "jealousy can be good for you." I distinguish envy from jealousy this way: Envy is wishing you had/did/could do what the other person has/did. This is a feeling I have a lot: I'll see someone doing sooo much better than I am at something -- characterization, language, style -- and I'll think, "IwishIwishIwish I were that good." I think this is healthy, because it gives me an aspiration. Maybe I can't be as good as she is, but I can try. I envy a lot of other writers: their talent, their discipline, their skill. And I try to become like them. I have a gazillion role models out there.
Jealousy, by contrast, is the feeling that the other person doesn't deserve her success, that it is rightfully yours, that there is something wrong about her having it. "Why is it her? It should be me!" Although I don't think I've experienced professional jealousy, I've sure felt romantic jealousy, and so I think I have a good idea of what the professional kind must be like. As everyone says, this emotion is corrosive and self-destructive When you think about it, it can't be anything else: when you must tear down the virtues and successes of the other person in order to bolster yourself, you proceed from an admission that your own work/virtue is so weak that it cannot survive except through such bolstering. It also externalizes achievement ("I cannot succeed because she's in the way") and consequently disempowers you.
(Let me take time out to address the issue of quality and success. We have all read works that were "successful" by some measure or other (that made a lot of money, got good reviews or had a huge audience) that we did not admire. Heck, during my Clarion class, we read aloud to each other from one such work, a best-selling novel whose sentences were so bad that we cringed. But such works are instructive (as one of our teachers pointed out) because they make the choices so plain. If you don't admire the work, then why on earth do you bother worrying about the fact that it made money? If you want to make money, being a writer is probably a bad idea in the first place. End of digression.)
But my own vice is regret. I started writing seriously rather late in life, and am the same age as some wonderful writers who have been practicing their craft for 20 or 30 years and who are now acknowledged to be at the top of their field. When I read their stuff, I get sick at heart -- not with jealousy, but with an awareness of time not spent wisely, of opportunities missed. I think to myself, "No matter how hard or well I work, no matter how much I improve, I'll never have the time to attain their skill." I feel something similar when I look at the glorious potential of my Clarion classmates, some of whom are young enough to be my own children and who are already so good. What would I have achieved if I had started at their age?
Regret is almost as corrosive as jealousy, and for the same reason: it's disempowering. When I get into a cycle like the one in the previous paragraph (and I love the sound of my own voice when I'm indulging in self pity), I externalize achievement. "Oh, I can't do as well as Kij or Kris because it's already too late" -- it gets me off the hook and takes away any present-time responsibility for my situation. Never mind finishing that first draft, buckling down to do the revision, or starting that novel - you can't win anyway.
As I say, I don't really believe in the ability to control your feelings. But I do believe in self-awareness and honesty about your feelings. As any therapist will tell you, your jealousy and my regret lose some of their power over us when we see them for what they are, see where they came from and see what they do to us. That's probably the best we can do.