How long is a page?

Mostly, I just decide to write.
I mean the moment before I then sit down to the computer and start writing.
I switch on the computer, open my files, maybe reread my notes or some of the actual text and then just continue or start another chapter of the book or make more notes.
But sometimes, after starting to write a couple of sentences, I just sit there and wait.
Wait for the page to be filled.
By some miracle magic something.
Okay - by me.
By my inspiration.
I want to be so immersed in the text and the thoughts and the moment within the book that I don´t even look-up, but just write and write and write.
I can always edit later.
But sometimes I just sit there and wait for the page to be filled.