I am jealous of certain poets/writers. It isn't really about their publication credits (outside of the very rare twinge) it is their quality of writing. I wish I could write like they do.
I believe I have brought this up before so, on we go...
Jealousy can be a good thing!
A little envy, channeled correctly, can force us to do better. It makes us take a look at our writing and try harder. I consider it fuel on top of already wanting to improve. Competition often springs from where we once felt jealous which is a good thing, in moderation.
Too much jealousy, though...
...can wreck a person. It makes you go forward when you don't want to/aren't ready. It turns you from a competent soul to a petty one. It drives you away from what made you love your art in the first place. You become a person even your dog wouldn't want to live with (and he has nowhere else to go).
So many writers are jealous to the point of destroying great friendships. They keep to themselves because they are paranoid sharing will lead to stealing or others somehow getting a peek at the competition and getting ahead.
We need to support one another, not just as writers, but as people. Every time one of us makes a huge sale, it should be seen as a victory. The publishing world (and world in general) is getting harder each day. We should cheer like crazy for each other, dance around when one of us finishes a book, smile and mean it.
Yes, there will be people out there who are still going to be petty and jealous to the point of no return. And yes, there will still be people who get published even when they're just a name and not a talent but that isn't our problem. Our problem is writing the best work we can and celebrating ourselves and each other.