The human body is a truly amazing machine. Against all odds, our bones, muscles, and organs work together to keep us alive, functioning in ways that we still don't fully understand. Consider, for just a moment, all of the events taking place within any of us right now. The heart is beating. The lungs are working to breathe. The brain is computing thousands of thoughts, sensations, and messages every second. The body is completely responsible for these functions, ensuring that they take place and that they succeed--and it's a good thing, too, because no one really knows how to voluntarily beat their own heart or control messages sent by the brain.
When it comes right down to it, we do very little to take care of our bodies considering how much they do for us. However, there are some occasions when the body demands more care, like after cardiac surgery--and on those occasions, rehabilitation is the answer.