Sometimes there are too many and they back up and congest as if in a traffic jam, all competing to arrive at their destination, their purpose, whatever that may be... incomplete and jumbled; some stuck on a round about, distracted, "Hey look kids, there's Big Ben..."
It's frustrating, this brain constipation, especially for one who writes. --Needs to write, like one needs to breath.
"A scrupulous writer in every sentence that he writes will ask himself... What am I trying to say? What words will express it?... And he probably asks himself... Could I put it more shortly? But you are not obliged to go to all this trouble. You can shirk it by simply throwing open your mind and letting the ready-made phrases come crowding in. They will construct your sentences for you — even think your thoughts for you to a certain extent — and at need they will perform the important service of partially concealing your meaning even from yourself."
...George Orwell, "Horizon", April, 1947