If anyone is a believer in solving challenges through sheer force of will, it's me. I'm a stubborn man and I am the son of an even more stubborn man. I don't believe in the word "quit" and I don't believe in giving up. I am however - as are you, finite. We all have limited resources. We get tired: physically, emotionally, spiritually. I have observed that there are moments we arrive at in problem solving where we have so depleted our personal resources that continuing to stare at a computer screen and carry on becomes counterproductive.