because hope springs eternal ? LOL...there is something in this actually. Reason it out. If you think the past is the best you can have what kind of stance can you have about the future if you've already experienced the best that life can offer...More of the same ,or something of an anti climax appear the best options. Neither on the face of it might seem to be an overwhelming motivational reason to get out of bed for most people. However , if they hope the best is yet to come then they're more likely to hit the carpet running Monday mornings don't you think. So we're talking about an explanation based in survival and motivation to do it. A maintenance of the body to enable it to keep on keeping on...sounds like a song coming on to me.