I’ve got chronic tendinitis in my hands, and I found that once I was able to isolate specifically what movement caused the pain (ex. How hard I was gripping things like pencils or utensils) then I could try to focus on not doing that, or find a brace/support that prevents that (ex. A thumb brace with a hard side to prevent me from moving it too much), then it’s just building the habit of wearing the brace before engaging in the activity that could cause aggravation