So I had some feedback about how punishing the stamina regeneration is.  It should be a penalty and something to consider, not a crippling penalty.  

I have had performance issues myself with the Windows version, no clue as to why. Either way, the regeneration rate was a bug and not intended.  It was not taking into consideration the frame processing delta.  I've fixed it up now and it should behave as intended even if there are framerate drops.

It should be all good now, but if there are any bugs please let me know.  Stamina regeneration while fatigued (red) should take just over 2 seconds.  It's slightly quicker when not fatigued.