There's jealousy... and there's jealousy.
If we didn't all have the capacity for jealousy, we'd be earthworms without knuckles or backbones, and the passion of our emotions wouldn't bite so deeply, capable of lifting us to rhapsodic heights and letting us fall into the abyss of misery. There's no point in blaming fire for burning the logs placed in the flames...
... and love wouldn't be love without the fires of jealousy.
(The weird thing is when jealousy springs up out of nothing, like a maggot looking for a corpse.)