Ooooh, that’s a nice description. Oh no no no, that’s a terrible way to put it. Oops, you wrote a passive verb. Hey, you just laid down three adverbs in a row! The right word just isn’t coming to me . . .
That pesky internal editor. Most writers say to lay down a bad first draft and edit later. There’s actually scientific reasoning behind it.
Right brain is creative stuff like writing prose and brainstorming. Left brain is editing your prose and sifting through which brainstorm ideas you should keep or chuck. When you use both at once--like brainstorming and editing at the same time--the brain can't keep up with the switching back and forth. Your creativity can stall or your analysis can be way off.
This is why many writers recommend turning off your "internal editor" when writing the first draft. Don't correct, don't second-guess that word, don't fiddle with that phrase, don't decide that action is too bland, don't stop and do research--just make a note and move on. That editing is left-brain work, which would short-circuit your creative right-brain work if you stopped to indulge in it.
So for some writers, it's best to only do creative stuff for one chunk of time--force yourself to be in that zen mode of writing or free association. Then switch to analysis of what you did. The times can be as short as five minutes each, but just make sure the activity times are clearly separated. This will improve efficiency when writing and developing a story.
One trick to try is closing your eyes. The senses of blind people sharpen to make up for loss of sight--your creativity might enhance when you remove your sense of sight. It can also remove the discouraging picture of the blank page. Block out distracting thoughts like work, housework, kids. If you can, type or write with your eyes closed, forget about misspelled words or the pen writing on the desk--oops, well, I guess you kind of have to watch out for that.
Another trick is to try writing as fast as you can. This forces you to just go with your gut and stall your analytical side. Plus this is often a necessity for busy writers with only fifteen minutes to write.
Also see my article Learning to get into the writing zone.