"I just don't love him/her anymore." That's a thing that we commonly hear nowadays in our culture. The married life requires a commitment to never let your love for one another die. But that's also how our love for our brothers and sisters in Christ should be. That's what Paul is talking about in this part of his letter to the Thessalonian church.
It's so easy for us to become complacent in our love for one another. But our motivation for love comes from Christ Himself. His commandment to us is that we love one another -- in the same way that He loved us. It's not easy. This kind of love is not the mushy kind of "love" that the world knows, where everything is about making ME happy. Christian love is all about putting others before self. It's about giving something which we know can never be paid back. That's how Jesus' love was -- it was overflowing!
John Calvin said that sacrificial love is the mark of a clean conscience. What are some ways in which we can show this kind of sacrificial love to our brothers and sisters in Christ, and to all around us?