Grip seems like a bad example since in most cases gripping something a little bit stronger will make your grip a little more robust to an unexpected perturbance (e.g. you stumble, or someone bumps into you). Unless you have good data on how common such perturbances are, how changes in grip strength affect robustness in the face of perturbance, and what drop rate is acceptable, how would you know whether you're gripping things too strongly?