Yogi Bera said: You can't hit and think at the same time.
I would amend that to say: You can't write and think at the same time.
By that I mean, sometimes (most times), your best writing will come when you don't think so hard about it - when you let it just flow out of you in a zenlike way.
That is certainly true for me.
I can feel when my writing sounds forced - when it doesn't flow well.
And those times are almost always the result of thinking too much.
Natalie Goldberg calls this writing with your monkey mind - as opposed to your wild mind (in her book, Wild Mind: Living the Writer's Life).
Katherine Paterson says: Send your inner critic off on vacation and just write the way little children play. You can't be judge and creator at the same time.
So my advice is to save your monkey mind for revising - but while you are creating, use your wild mind.
Don't think too hard about it.