Relax any time you need to relax. This sense of serenity will help you to concentrate, and keep your brain functioning at its best.
The slightest feeling of nervousness will simply cause you to relax, and you can stay calm every day, in every situation.
Repeat these relaxation exercises as many times as you like to prepare for high pressure situations. When you relax, these situations can feel much less stressful.
Breathe deeply. Relax your muscles. Calm your thoughts.