Mousing while resting on a wrist rest is not ideal. Using wrist rests can significantly increase the pressure inside the carpal tunnel. Further, wrist rests compress the finger flexor muscles.
Do not use a wrist rest for the mouse. Also, do not rest your elbow or lean your forearm on a chair arm rest while mousing.
Instead, take breaks from mousing. It is OK to use the arm rests to rest in when not actively mousing or typing.