This section is from the "Nature Cure: Philosophy and Practice Based on the Unity of Disease and Cure" book, by Henry Lindlahr.
At first glance this expression may seem paradoxical, but experience will teach that it is not only possible, but absolutely necessary that we perform our work in a relaxed and serene condition of body and mind. The most strenuous physical or mental labor will then not cause as much exhaustion as light work done in a state of nervous tension, irritability, fretfulness or worry.
Relaxation while working necessitates planning and system. Most nervous breakdowns result not so much from overwork as from the vitality wasted through lack of orderly procedure. Therefore, take some time to plan and arrange your work and form the habit of doing certain things that have to be done every day as nearly as possible in the same way (making sure that it is the right way) and at the same time of the day. Such orderly system will soon become habitual and result in saving much valuable time and energy.
Always cultivate a serene and cheerful attitude of mind and soul, taking whatever comes as part of the day's work, doing your best under the circumstances, but absolutely refusing to worry and fret about anything. Do not cross a bridge before you get to it, and do not waste time regretting something that cannot be undone.