This is the thing that always gets to me. I generally have a plan of what major events are going to happen and where but when it comes down to just getting the story to advance to those points, I can find myself without much motivation to do it. More often than not, I find myself excited to write events that should generally be a while away chronologically rather than continuing in the correct order.
Although saying that, sometimes I suddenly come up with other story ideas during the 'in-between chapters' that I really want to incorporate into the rest of the story but they can throw everything else off a bit. So a lot of the time it's trying to find the balance between not cramming too much into one story but still putting enough in for it to be interesting.