When Paul says "Love does not envy" he is addressing the earnestness of our desire. A strong or intense desire is not necessarily a bad thing. In fact, Scripture tells us to "earnestly desire" higher spiritual gifts among other things (1Cor 12.31). But if we desire or love something in the wrong way and to the wrong degree, then we have entered into the realm of envy. The darkness of envy will not rest until it has snuffed out its rival, even if that rival is the "light of the world."