Productivity (or the lack thereof)
If you ever want to feel utterly unproductive, and like completely wasting your time - try spreading rock in your yard. We ordered 10 cubic yards a while back, and I can spend an afernoon moving rock, 10, 20, 30 wheelbarrows - and, at the end of the day, I'm hot, sweaty, sore as hell - and that %&*$ pile that was 10 cubic yards looks pretty much unchanged.