One of the best pieces of advice I got on writing is the importance of writing without editing. Which means, turn off the inner-censor in your mind and write freely.
What or who is the “inner censor”? Well, the inner-censor is the little voice in your head which tells you “Oh don’t do that, that’s stupid. That sounds stupid. That looks stupid.” It is that inner-voice that prevents you from writing in a stream-of-consciousness flow.