I also got this message, partway through a longer fight. My health was 100%, green bar was around 80% but mental stamina was down below 20%. Thought it was really odd, cause it wasn\'t THAT long a fight, and i\'d gotten in longer ones without triggering that message before.
So.. probably a rebalancing needed. Although it makes sense to have your mental grip slipping in a long fight, that\'s no reason for you to STOP fighting. (Especially if your physical stamina is ok). It ought to lower your abilities instead. Make it harder to evade, harder to hit, less accurate cause you can\'t focus, things like that.