Over time you let things slip, you get sloppy, and you wake up one day, and your work is lackluster. There is no choice to getting worse at something; you simply choose to stop getting better at it.
Getting better happens fast. The start is right now, and it is immediate. There is no slow, creeping wall of carelessness or complacency.
You start working on getting better, and you will instantly begin to get better and forming habits, which will be like force multipliers to you continuing to get better.