On the (unfortunately) few, rare occasions I've actually pushed myself to my limits (physical, mental, emotional, or otherwise), I've felt more of a sense of accomplishment and a drive to push further, in any of those domains, not just the one I pushed in, than I've ever had before. I certainly wouldn't claim to have anything figured out in the realm except on a personal level, but for me, every time I achieve something that seemed unachievable it's like it unlocks something in every other part of my life.