It's easier to get complacent and lax, I think. As in, not pay attention because you "know" how. Unfortunately, losing 5 pounds still takes just as long the second time as the first time.
On the other hand, once you actually get back on plan, it's a lot easier to stay on because it's second nature. You know that if you stick with it, it will work.
Definitely a balancing act.
Jay