These are the things that have helped me, roughly in order of effectiveness: 1. "Stop doing that". Fix your ergonomics, change your keyboard, and take breaks

These are the things that have helped me, roughly in order of effectiveness: 1. "Stop doing that". Fix your ergonomics, change your keyboard, and take breaks until the pain goes away. 2. A good physical therapist will help you root cause the problem and fix up major issues 3. Strength training, even just minor exercises for that wrist and arm. Eccentrics seem to be the one of the few things that really helps tendonitis. 4. Reduce stress. Somehow stress seems to exacerbate all of these problems.