For every new habit I try to form it takes longer than I expect for it to cement. The first few days or weeks might be a breeze where it comes easy and I get it done every day. Then some disruption hits and I pause because I have no other choice of course.
Once that pause happens it can be really difficult to get back into it. I'll start again tomorrow. Nah I'll start next Monday, for the new week. You know what? The month's almost over, I might as well start again from the first of next month.
It's a bit of complacency that sets in after that early rhythm. It's easy to become confident that the new habit has already formed when everything is going smoothly. What I've realised is the true test is when things aren't so smooth. When your usual schedules are interrupted, do you keep going or take a break?
I think a properly formed habit can almost effortlessly survive an interruption. When you finally get back to your typical rhythm it returns with it. To get to that point requires maintaining a lot of focus and not getting too complacent. It can take just one day to be back to square one.