Anger, especially chronic anger, often leads to muscle tension, stiffness, and soreness. One approach to dealing with such tension is to stretch out those areas you tend to carry such tension (shoulders, neck, etc.).
There’s three steps to this process: (1) Identify your tension areas. Where, specifically, do you tend to get tight when you are frustrated. (2) Adopt a more comfortable and less tight posture. (3) Actively stretch those areas that are uncomfortable.