Efficiency is highly overrated; Goofing off is highly underrated. Regularly scheduled sabbaths, sabbaticals, vacations, breaks, aimless walks and time off are essential for top performance of any kind. The best work ethic requires a good rest ethic.

Source: Kevin Kelly: 103 Bits of Advice I Wish I Had Known

I feel this. I am conciously making an effort to get up and just walk around instead of always being still, at my desk.