Desk Doctor is constantly checking to see if you are holding the mouse but not using it to point and click (‘hovering’). If so the Desk Doctor Health Monitor prompts you to let go of the mouse, by showing a red mouse symbol.
Desk Doctor reminds you to let go of the mouse.
Grasping the mouse while just reading or thinking is a very common bad habit while using a computer. Unfortunately, this can quickly, though unconsciously, build up a lot of muscle tension, which, over time can cause the painful symptoms of RSI (repetitive strain injury). Therefore Desk Doctor reminds you take the opportunity for a natural break; to let go the mouse and let your muscles relax.