Are you more likely to compare yourself to those who "have" more than you or to those who "have" less?
Even though one comparison has the effect of making one feel dissatisfied, I would wager that we choose this comparison far more than the other.
When you compare your situation to those who "have" less, naturally one feels grateful, blessed, lucky, and content. (And as a bonus, a little thing called compassion starts growing inside.)
So clearly, there is a superior choice here.
Why, as human beings, do we choose the comparison that provokes ill-feelings?