Fandango’s provocative question is: “Is jealousy purely a negative and potentially destructive emotion, or does jealousy have any value as a motivator to drive people to improve themselves?” This really comes down to semantics and what we mean by jealousy. If by the term you mean a possessiveness of things, and especially of people – then it is a destructive thing. To be jealous of one’s partner presupposes “ownership.” Trust and partnership should ideally be the foundations of a relationship, not control.
This does not mean we aren’t hurt if said loved one goes elsewhere for affection, but that is their choice. The third party, however, did not “steal” your love interest. So in that way, Fandango’s “motivator” point may come into play. We should be the best us – if we want to be in a relationship with the best them. But again, this is not ownership, it is making oneself desirable, not the controlling a partner’s life.
If on the other hand by jealousy we mean covetousness or envy, then it still has negative connotations as it can distort our values. To begrudge others possessions (here we are speaking of material things, not people) or position then we are being unfair as they too have aspirations and needs. If we desire another’s attainments and do so without real effort to achieve our own, then it is wrong. While many things in life are finite: gold, etc. They are still abundant enough to be sought after. So in this way Fandango’s “motivator” still comes into play. But empty “envy” which “wants,” but does not seek to achieve; that wishes misfortune on others for our own satisfaction or ends – this is wrong.
By the way, honour and accomplishment are not finite. There is enough honour to go around for those who are honourable.
All in all, wanting to gain something is a motivating force, but it should never be done with malice or at the expense of another.