Mental or physical training?

As I head out for my 8 miles, I begin to think about the whole training process. Here I am in the middle of the week with the most mileage and wonder what this training is really for. At this point, there is no question as to whether my legs or lungs will make it to the finish line. (Knock on wood) They may have their moments, but I know they'll be there through it all. The question is whether my mind will be there or not. I've come to the realization that this isn't about running, it's about mind over matter. The long runs are a test for the real deal when you don't want to go another step, but convince yourself there is no giving in now. It's having hit the wall several times in the months previous and knowing that if you got past it then you sure aren't throwing in the towel on race day. As one foot goes in front of the other and I finish what's allotted for me I think I finally see the bigger picture. How mentally tough am I?