First, what I have done right is blast out 40,000 words in 20 days putting me ahead of schedule and confident of hitting the goal. Interestingly, at least to me, I think 50,000 words will be all the story needs; that is, this one will be novella length and probably less than 50,000 when revised and edited.
So, what have I ‘done wrong’ to maintain this speed?
Used lazy cliched expressions; I haven’t quite sunk to ‘speaking through clenched teeth’ or ‘the clouds were like fluffy white sheep gambolling in the sky’, but I’ve given the cliche tree a good shake.
Sprayed adverbs like a child with a can of paint on a white wall – the school of ‘she crept slowly and quietly along the dark and gloomy lane, the trees hanging limply – ‘ well, you get the idea. Sure keeps up the word count!
Instead of hesitating whether ‘resolved’ or ‘decided’ is the most appropriate word and getting sidetracked in the process, I write ‘thought’ and hurry onwards. Revision comes later.
When arriving at a complex plot point, instead of hesitating etc as above, I think of any dramatic development and hurry onwards as above etc. I killed off a main character yesterday, much to my surprise and you know what, it works. If I’d pondered and procrastinated, I suspect I would not have done so and the novel would be the poorer for it.

Finally, it brings back the good old days when I wrote my PhD at top speed to crazy deadlines after three years of surfing and partying instead of doing much actual research. A much maligned skill which appears to have lasted a lifetime!
All’s well that ends well as an actual great writer once said.