Typing and hand-eye coordination?

I am a pretty average typist, and I have a question. I can usually type words without looking at the keyboard, but for some reason when I TRY typing without looking at the keyboard I almost always make mistakes. Basically I have to be unaware that I am not looking at the keyboard to be able to type without looking at the keyboard. To those who understood my words, why does this happen? I'm sensing a psychological answer so I put this in that category