How can horses know this??? plz answer?

i went on this trail riding thing last weekend on a VERY hugh mountain, the trail was skinny and it made really TIGHT turns (about 8or 9 times or so), like you would go down and take a turn that make a half circle then came back parralel to where you just started the turn. My horse didnt break a sweat (unlike me), he went on the VERY edge of the cliff, and didnt loose a step!!! He got mad at me for trying to get him in the middle of the trail all the time!! haha. But, how do horses know EXACTLY where to step? Mostly with out worrying!! :)