Intensity of task matters the most

To get the best results in your fitness, research has found that shorter but more intensive exercise is more effective than longer drawn-out exercise.

The concept is simple: Intensive activity followed by high quality rest and recovery.

Most of the growth actually comes during the recovery process. However, the only way to truly recover is by actually pushing yourself to exhaustion during the workout.

The same concept applies to work. The best work happens in short intensive spurts. By short, I'm talking 1-3 hours. But this must be "Deep Work," with no distractions, just like an intensive workout is non-stop. Interestingly, your best work - which for most people is thinking - will actually happen while you're away from your work, "recovering."