Fortitude

The measure of your heartiness and ability to withstand pain and suffering.

0: You flinch when you are hurt.
1: There is a good chance you'll keep fighting when you are hurt in combat.
2: You keep on going, even though you've been pretty seriously wounded.
3: You can easily shrug off the feeling of fainting after grievous wounds.
4: You might even tell entertaining jokes while under extreme amounts of pain.
5: The interrogator's tricks don't seem to be working as you grin and bare the pain easily.
6: I heard once that he lost both arms and still kept fighting!