Well, heh. To be 100% honest with all, I have two reactions.
There's the knee-jerk reaction, which was stronger when I was younger like all emotional reactions were, which is the reaction that is visceral, hateful, spiteful, "I could do better," "I've written more lyrical sentences," "I've looked in my bedroom mirror and seen a hotter face/figure..." and all of a sudden, I feel this deep well of hot molten something bubbling up in my gut. That person wouldn't be on my radar except that they have something I believe to be undeserved. And I believe I deserve it more. That's the horrible ugly truth within me, and I hate it.
Then there's a second reaction that usually follows the first, a sort of "talking myself down" reaction, where I remind myself I'm not ever in competition with anyone except my past self. And the jealousy (let's call a spade a spade) within me, if left to fester, is a poison. And I have things to offer, and a story to tell, and a life to lead, that jealousy and opinion seeking and status anxiety wil only ever warp and inhibit. Mostly I do well reining that ugliness in. But man, that demon chases me sometimes.
That's the whole truth.