Mind over Body (Original) p. 64
Your training and mental toughness allow you to use your focus to overcome physical threats. By focusing your mind, you ignore the effect of a deadly poison or debilitating sickness.
Your diligent training and intense mental focus combine to allow you to overcome physical threats with the raw power of your mind.
You can use this maneuver any time you would be required to make a Fortitude save. Make a Concentration check instead of the Fortitude save and use the result of that check to determine the save's success. You must use this maneuver before you attempt the Fortitude save. A result of a natural 1 on your Concentration check is not an automatic failure.