"Not to get too deep here, but the most valuable thing I can think of is to be grateful for suffering. That is a sublime feeling, and completely inexplicable and illogical, but no one doesn't suffer. So the degree to which you can be aware of your own humanity is the degree to which you can accept, with open eyes, your suffering. To be grateful for your suffering is to be grateful for your humanity, because what else are you going to do - say, "No Thanks"? It's there. "Smile and accept", said Mother Teresa. And she was talking to people who had it rough."
Believe it or not this quote is from a Rolling Stone interview with T.V. personality Stephen Colbert. I was reading the magazine on the way back from Hawaii and when I came across this answer I thought to myself there it is. I am often asked how I manage to push through pain in races and I think the way he describes suffering is the best way to answer it; acceptance! I spend the last few days before a race preparing myself for the fact that I know it is going to hurt and I am going to suffer. Once you have come to terms with it in your mind you can accept it and there is something quite magical about that.