I've seen people workout at 4:10am before working two to three jobs. I've known introverts who became great communicator when an important relationship needed it. I've seen who weren't "Ready" suddenly commit to the right person. People gives effort to what's important to them.
Cheating simply means that you chose sex over the person that you love. It means, so many people, more people are choosing sex over love. But they would not care to accept that fact.
Blaqbonez is right