The enthusiasm drops. That's how things start to decay.
It can be in anything: your habits, your connections, even your outlook. One day you are reliable; the next you avoid a little, then more. Before you realize it, what you constructed is beginning to collapse.
But there is good news: If you see it, can be repaired. Since things do not totally disintegrate overnight, they may also be gradually restored. Honesty admits something is wrong, whereas discipline flips it around.
Because the reality is nothing holds solid by chance. It gradually starts to disintegrate the moment you stop working on it.