Ultramarathons have a way of beating you up. It's 32 miles of pure suffering. All the outside layers are peeled off like an onion and you are left with your doubts and fears and a finish line that seems like a millenium away. But step after step, mile after mile, hour after hour, you finally reach the finish line and all your doubts and fears vanish. I've entered three ultras and by the sheer grace of God finished all three.
The keys are:
1. Monitor your pace so that you have enough energy to get you to the finish line.
2. Try to ignore your brain when it tells you -- begs you! -- to stop.
A lot like life isn't it?