And with each sprint, I strive to take as much pain as I can before I am forced to slow down.

It is not pain I seek. Pain is simply the symptom of lactic acid accumulating in my muscles, and I have to teach my body to handle lactic acid in races. You could as much say that I like lactic acid as suggest I like pain. 

Pain is to be used. At times, it warns me I am doing something wrong. At other times, it signals I am doing right.

If I am driving for the finish of a race and there is no pain, I know I have not yet pushed my body to its absolute limit. On the other hand, there is pain that commands to go this fast and no faster.

The runner is not a masochist. The runner does not enjoy pain. But between the runner and a personal best lies pain in quantity, both in training and in the race. And the pain, once endured, comes to have a value of its own. I do not seek suffering, but once it has been experienced, I feel somehow the better for it.