Why is it so difficult to do work when we are not prodded?

I don’t know too much about psychology. I guess this question has more to do with human nature and perhaps even evolution. Why is it difficult by nature to do the things we know we should do, to do work? Was there (ever) some benefit to sitting on our butts? It seems to me that we should be predisposed to get things done, to be doing all the time. I understand the argument that if it were easy, everyone would do it. So shouldn’t this motivate us more and become a self-sustaining competitive cycle whereby we try to outdo each other and get as much “work” done as possible. By work I mean anything that would be beneficial to us but that is not enjoyable to do – cleaning, studying, job searching, etc.

I wish that I would behave by doing what needed to be done as soon as the thought entered my mind. I am only a fraction of my potential otherwise. Do some people have this type of control over themselves? Are they masochists? Am I the only one that spends more time thinking about doing rather than actually doing?
– Unfulfilled Potential