Pacing oneself for high performance

I had a conversation today with a colleague about the need to pace oneself, when there's lots of new development work to do on products and services or other things, in the midst of current work on the go and maintaining networks and connections and responding to enquiries etc, etc. Development work requires dedicated thinking time and planning time and it can be tiring, having an intense focus for long periods of time. The key to prevent serious mental fatigue is to mix times of high focus and intense demand with periods of less demanding work. It's like an athlete's high performance training programme: bursts of high intensity, endurance building stuff with more gentle workouts, in-between. As it works well in the sporting arena, why not in the business arena as well?