Just concentrate on your breathing. After 10 to 15 minutes, open your eyes. Remain seated for two to three minutes. Resume your normal activity. Tense, then relax.
Progressive relaxation is a popular relaxation technique that has been used for years.
The idea is first to tense, then to relax, specific muscle groups in a regular order. Lie on the floor. Remove your shoes. Close your eyes and breathe normally. For each muscle group, tense the muscles for six seconds, then relax.