It might seem like you're only writing when you're filling pages with text, but writing and typing are not the same thing.
Most of the writing process is simply thinking. Thinking about the ideas you want to express, the structure, the way one idea leads to or follows on from another.
When I sit down to write, I'll spend extended periods just staring out of the window while I juggle words and ideas in my head. But this, too, is only part of it.
It's often in the times when I'm nowhere near a computer that the real writing happens. It's while walking or commuting or doing anything else that lets my brain run free.
It's creative, rather than productive, time. And, for me at least, it's essential.
So don't think of writing as just typing. Take the pressure off and give yourself time to think.