As a reaction, which you take when you make a Fortitude saving throw, you can focus your mind to overcome physical pain and control your body’s response. Until the start of your next turn, including against the triggering saving throw, you have a +1 bonus to Fortitude saving throws.
You can use this maneuver before or after making the saving throw, but before any effects of the saving throw are applied.
You can expend 1 additional stamina to increase the bonus by 1.
You can expend 2 additional stamina to increase the bonus by 2.