To write efficiently, you need to call upon your writing voice.
If you are not in tune with your inner writing voice, then you can lose track of how the prose flows and sounds. But when you use your writing voice, you kind of narrate as you go along, which helps you to gauge if your writing is good enough. In other words, you are being both the writer and the reader at the same time.
I’m not suggesting, of course, that you read out loud. Just acknowledge what you’re writing in your head, rather than just spewing any old nonsense onto the page. Authors speak in a certain way on the page, which differs from how people speak orally, so it’s important to get into that zone.
On days when my writing voice is absent, I find it very difficult to string sentences together and produce quality writing. To remedy this, I usually grab a notepad and do a writing warm-up, spewing words onto the page until the sentences become more coherent and I rediscover my writing voice.