'Sleep faster, we need the pillows!' exhorts a Polish saying. But some things have their own natural pace or rhythm. One of these is the so-called circadian rhythm, which is the 24-hour cycle that makes us feel sleepy at night and wakes us up in the morning. A less well known one is the ultradian rhythm, which is a cycle of alternating dominance of the left and right hemispheres of the brain during the day. The left hemisphere, which specializes in logical, linear thinking, is dominant for around 90 minutes and then the right hemisphere, which processes non-verbal, daydreamy kind of thinking, is dominant for around 20 minutes and so on throughout the day.
You can often see this in the workplace where, after about 90 minutes of focused work, people lose concentration and find their mind drifting off. Some will stare blankly out of the window or at their computer screen; others will go and smoke a cigarette or make a cup of coffee -- observe your colleagues! They are following (albeit rather ineffectively) their need for a period of daydreamy right hemispheric dominance. The increased concentration they experience afterwards is to a significant extent caused not by the nicotine, caffeine, or whatever but by the brief period of restorative right-hemispheric activity.
Formula 1 drivers know that although a pit stop costs time, the benefits more than make up for it. The better you learn to utilize your periods of right hemispheric dominance, the more effective you will subsequently be able to be. There are many ways to do it. One easy way is to get comfortable, close your eyes, consciously relax each of your muscles in turn, and indulge in recalling an enjoyable memory or imagining. Twenty minutes is ideal but a few minutes is much, much better than none.
Try it next time you feel your mind drifting off. You'll feel great and find you need less nicotine/caffeine/biscuits too. And the more you practice, the better it'll be!