Surveys have been done on this, adding up the amount of time an average guy spends in his lifetime studying, working, watching TV, waiting in queue, waiting at the traffic light, eating, sleeping etc. and finding out actually how much time he's really awake and living meaningfully.
Recently I find myself mulling over the same thing over and over again, so much so that I'm plagued by those thoughts even in my dreams. It's about things that had happened in the past.
Then it dawns on me how much time I've spent (wasted) living in the past instead of cherishing the present. Eleanor Roosevelt said, "Yesterday is history. Tomorrow is a mystery. Today is a gift. That's why it is called the present."
Yes, like the determined orang utan in the picture, I shall live in the present from now on!