It is true that there are times when the ideas don't flow as smoothly as at others but I find that conversing with ones characters helps.
Someone, I forget whether it was a writing friend or a famous author, once said that writer's block occurs when the characters stop talking to you. I can see that after a number of years of writing, but wouldn't have known what was meant prior to being involved in the art. In fact I might have gone further and said that people talking to their fictitious creations were nuts! In which case I joined that clan 7 years ago.
Of course it must be remembered that a conversation is a two way street and if you don't talk to them they won't reciprocate. Quite often our side of the conversation is about significant moments.
Those moments can be as diverse as a proposal, ranging through to to theft or murder but whichever you choose causes your characters to react. In Cessation the significant moment upon which the whole story was based was the failure of the production of electricity across the whole of the UK. Now that was only the beginning in fact there were many more 'moments' before the book was finished.
What I have found is that having these points in your story can speed up or slow down the flow of your writing. These points in your writing are forming characters reactions and their history so that reality is bred into something that you have created. I chose Cessation as an example because all of the characters were new to me, unlike the 9 previous Steele novels. The moments I created were not centred on crime, well not all, but on human relations and hardships, but the reality was in the closeness of the basic premise of no electricity, to what was happening in the country at the time of writing.
The Steele novels present a different challenge in that the links between the books and reality were, in the beginning, more tenuous and so were the 'moments' of significance. Of late, with my tendency to adopt a more cynical view of authority and therefore lean towards the possible truths hidden from the world, the adventures of Patrick Steele have become closer linked with reality. Even so, when in doubt, I can always throw in a creative spanner that energises the story.
I have never considered myself an analyser of stories and the literary art, but as one wades through the shadowy corridors of writing understanding of what you are really doing deepens. It is a fascinating journey.