In a word, bad relationships are "destructive." In two words, they are "completely destructive.

It is far easier to strengthen a strong relationship even more than to strengthen a relationship that has soured. Better to prevent ruining a relationship than trying to repair it.

Enjoy your cake while the frosting on it is fresh and moist. Once the frosting stales and crack, the cake ain't taste so good.

Rarely, if ever, does our conscience realizes the crisis our evil deeds cause. Seems the human mind is wired to find joy in another's misfortune. The Germans call it Schadenfreude.