Writing: there is plenty evidence that writing about stressful events can help relieve stress and improve diseases linked to stress. Write for 10-15 minutes a day about stressful events and how you felt. One way is by keeping a stress journal. This can help you identify what’s stressing you out in life so that you can find better ways to cope with them.
Expressing your feelings: Discussing how you feel with family, friends or even a counselor is a very important way of coping with and relieving stress. Laughing and crying is also very good for you, it releases tension and frustration. They are both part of a normal emotional healing process.
Mindfulness Activities: they help you relax your mind and are often combined with body centered relaxation exercises. 
      • Autogenic training- it consists of six standard exercises that make the body relax. And for each exercise you use visual imagination and verbal cues to relax your body in some specific way. 
      • Self-hypnosis- can open your mind to suggestions that can relieve stress or change the way you respond to stress.
      • Meditation- focuses your attention on feeling calm and having a clear awareness about your life. 
      • Guided imagery- (visualization) is a method of using your imagination to help you relax and release tension caused by stress. Your body responds to the images in your mind. Use these simple imagery exercises for relaxing or renewing your energy when you need to relax. 
      • Music therapy- can relax your body, improve your mood, and change the pace of your day. 
      • Humor therapy- it reduces stress and even boosts the body’s immune system.

I've noticed when I laugh while I'm stressed out I feel a lot better. Even if its just at stupid things like watching a funny show or people falling on youtube, it makes me laugh and I feel a lot better and less stressed out.