When you're trying to write, it can be frustrating if the words don't start flowing straight away. But getting frustrated doesn't help. It's better to relax into the writing with a calm, focused mind.
Neil Gaiman has a simple rule to help with this:
You don’t have to write. You have permission to not write, but you don’t have permission to do anything else.
This takes the pressure off. It gives you time to think, to daydream, to juggle ideas in your head.
More importantly, perhaps, it lets you experience the slight discomfort of not producing.
I would go down to my lovely little gazebo at the bottom of the garden, sit down, and I’m absolutely allowed not to do anything. I’m allowed to sit at my desk, I’m allowed to stare out at the world, I’m allowed to do anything I like, as long as it isn’t anything. Not allowed to do a crossword, not allowed to read a book, not allowed to phone a friend, not allowed to make a clay model of something. All I’m allowed to do is absolutely nothing, or write.
I’m giving myself permission to write or not write, but writing is actually more interesting than doing nothing after a while. You sit there and you’ve been staring out the window now for five minutes, and it kind of loses its charm. You’re going, “Well, actually, let’s write something.”
Write, or don't write, but don't do anything else.
Quote Source: Neil Gaiman interview on the Tim Ferriss Podcast