There comes a point about mid-way through writing a pocket novel (or indeed any novel) when I hit what I call 'a wall'. To me it's a bit like the wall encountered by marathon runners when half way through the long race they feel they simply can't go any further. Of course they do manage to run through it and finish the race and likewise I do manage to get on and finish my 50,000 words but it's not a nice feeling.
Now that I have written six PN I know that I will get that 'wall' every time and I'm ready for it. At this point, one can do several things: give up on the story and start something else (I did this a few times early on only to discover it happening all over again!), give up writing for a while (did this too but only wasted time), write XXX and go on to a pivotal scene or a dramatic bit that's exciting to write (this doesn't work for me as I have to start-middle-end with no dotting about) or simply wade on, scale the wall slowly and painfully and drop down the other side before steaming on to the end.
I scale the wall. It's not pleasant but if I plod on I always reach the other side and I can edit what I've done later on.