It seems to me that if you are alive and breathing, you have some level of stress in your life. While we know much of this stress is self imposed, it exists none the less. Reason 4 for smiling: stress relief. Stress can manifest itself in many ways but it can be most evident to others in your facial expression. Smiling can help prevent you from looking tired, worn, down, and overwhelmed. When stressed, try to relax those face muscles and take time to try on a smile.