Our world says love is basically a transaction of self-fulfillment. You stay in a love relationship as long as both sides profit from it. However, when the costs outweigh the benefits, you just cut your losses and move on. But that is not Christian love. In Christ, we know that all life-changing love is substitutionary sacrifice. That is what Jesus did for us on the cross and that is what He gives us the power to do when we are in Him.