I'm not sure if you run into this as often as I do. You're writing along, and you write a line and the narrative seems to stop. Suddenly you can't think of a way to start the very next sentence. Sometimes you stare at it, and sometimes you walk away, but when you break that block, you realize the problem was in the last sentence you wrote: it was "turned back" toward the previous text rather than being "turned forward" toward the next part of the story. Once you change it and turn it forward, the next sentence appears with no trouble.
Transitions can be tricky. So what is it that "turns" a sentence forward rather than backward?
The answer is in the content - but that's too vague to be much use, so I'm going to consider a couple of examples from my day of editing.
I've been working with integrating existing material for a chapter with new material that takes the ending in a different direction. In the existing material, a newly hired servant (Aloran) gets introduced to his new colleagues and shown his quarters, but when he realizes he's not fully prepared, he's too frightened to ask his mistress permission to go out and get new supplies. In the new ending, one of the things he needs in order to be prepared is to take her measurements for a pair of gloves, so in the end he must go back to face her despite his fear.
Here are the two lines where my scene ground to a halt:
Every member of the Pelismara society in a single room pressing hands, when one of their own had just died of Kinders fever? How could he stop Lady Tamelera from touching anyone?
These lines set up a significant question - the question of how to take Lady Tamelera safely to a party where disease might be passed around. However, they could serve quite well as the cliff-hanger ending of a chapter. I think this is because there's the declaration of a serious problem that Aloran will face at an upcoming event, but no hint of what solution he might need. Thus the final sentence has a threatening ring - perfect for a cliffhanger ending that will send readers forward across a chapter break looking for an answer, but not so good for a smooth shift of the chapter into the next section where Aloran pursues a solution. I therefore revised it as follows:
Every member of the Pelismara society in a single room pressing hands, when one of their own had just died of Kinders fever? With that kind of contagion risk, he'd be tempted to wear his treatment gloves.
Suddenly I had the way forward. The sentence about contagion risk references Aloran's medical training, and in that context the solution is obvious to him. The idea of "gloves" appears right where it needs to, and can easily be extended conceptually from "I should wear gloves to protect myself" to "I should get my Lady to wear gloves to protect herself." That's a motive he can act upon right away.
I ran into another block in a spot where Aloran decides to leave his room (because he wants to figure out what she'll be wearing, so he can make gloves to match). He faces a decision of whether to exit into his Lady's room or not:
He found his service speaker and flicked it on, but heard only silence in his Lady's chamber. If he opened the small door with the crescent-moon handle, he could go and study her wardrobe. But if she were still there, sitting quietly, she would be angry because she wanted to be alone. Lady Tamelera, angry.
In the earlier draft, his next thought had grown directly out of the idea of her anger; he'd decided he had to get away from the whole situation. This no longer fit with the requirement that he deal with her in the course of the chapter. After some thinking I decided that he was too rattled just to steel himself and go in, but that he could ask for help from someone who knows her better. I could have continued with "He went looking for Serjer," but I wanted to use a word-link to smooth the transition. In this case, since there are two doors out of Aloran's room, I chose opening the door as the link. The next line became:
He opened the door into the Maze, and went looking for Serjer.
This created an explicit parallel between "If he opened the small door with the crescent moon handle" and "He opened the door into the Maze", thus bringing attention to the fact that in the end he decided not to open his Lady's door.
I enjoyed working through this material and trying to create links where there had been none before. It put me in mind of something I learned about when I studied classical Japanese poetry: the idea of a "kakekotoba," or pivot word. A pivot word has two meanings. It serves as a pivot because one of its meanings should fit with the lines of poetry that precede it, but its other meaning should fit with the lines that follow it. If, for example, the pivot word were "matsu," then on one side of it we should find lines that speak of pine trees (matsu=pine), and on the other side, lines that talk about waiting (matsu=to wait). This concept spoke to me, because in each of these cases I could identify a critical element that allowed me to make the link forward to the next section: gloves, in the first instance, and the door in the second.
I suppose the main things I took out of this afternoon's editing were these:
1. The implication of a large unsolved problem is good for a cliffhanger, but not for a minor transition.
2. At the end of a sub-scene, consider "seeding" a motive for the sub-scene that follows, in order to smooth the transition.
3. If the implications of the last sentence you wrote seem to take you in the wrong direction, look back further, because you may find something you can use to turn the text the way you want it to go.