In our journey to get better every day, it's easy to get lulled into a false sense of complacency. You can feel like you've established one new habit and now it's time to move onto another. Truly forming a habit takes continued effort and surviving many unexpected obstacles. Even when you've been successful at it for a while all it takes is a few days off the wagon before it's lost completely.
The rhythm you establish for a habit can be easily broken. You might take a week vacation, or be busy with some project and suddenly your schedule isn't the same. Maybe your goal was to write every day and you always write at 10 AM. But for the next week, you're in another country, the time zone is different, and you want to have fun. When you get back home it can be hard to reestablish that rhythm and the longer you forsake it, the likelier you are to lose that new habit altogether.
Getting out of my schedule every so often helps me combat this complacency. Rather than having a big event shake my life up and I'm completely unprepared, I prepare myself through small deviations to my schedule. Gradually I think I've gotten used to unplanned schedule changes. While I might miss a day of my habit I have an easier time restarting the following day.