Let out the air and as you do visualize the air as being all the pent up stress. It is very important that one has something useful to do during the day and to stay occupied. An hour to a nervous person seems like forever. It is essential that a nervous person has outside interest so that time passes quickly. Breathing into a paper bag and then rebreathing the air in the bag can be relaxing.
Meditation is another helpful tool.
Find a comfortable place to sit. And be as quite as possible and there should be no distractions. Clear your mind. While you're meditating its nice to listen to some relaxing music such as Classical or New Age. Try to do this for at least fifteen minutes a day.