Since doing copywriting and editing the last few years, I have had to retrain myself in the way I think, or in this case, how not to think. When I first began putting the words to paper for my novel in progress, each sentence became a painstaking ordeal. I rewrote that sentence way too many times until it was just right.
Now sure, the sentence is the best it can be but at that rate, it would take me one hundred years to complete my manuscript. I had to put away the editor in me, that little voice of perfection, and just write the story that wanted to be told.
I had to ignore the cold sweats and shaking hands as I typed away improper sentences, fluctuations from past to present tenses and changes in viewpoint. Instead, I had to force myself not to hit the backspace button, but to continue on my way.
It wasn't easy but it was definitely worth it.
I am currently closing in on the halfway mark of my word count and the story is coming along nicely. I may have lost a lot of the flow I wanted in it had I nitpicked my way through every sentence.
Plus, that is what the second and third, and possibly the fourth, draft is for. Once the story is out, complete in characters, plot and substance, then you can go back and work on the inconsistencies, sentence structure and grammar.
So far, this has been the best and most useful advice. Don't think. Just write!