You are significantly tougher than normal.
Base Fortitude save bonus +2,
You gain a number of hit points equal to your current Hit Dice. Each time you gain a Hit Die (such as by gaining a level), you gain 1 additional hit point. If you lose a Hit Die (such as by losing a level), you lose 1 hit point permanently.
A fighter can select Toughness as one of his bonus feats.
[*Behaves remarkable similar to the Improved Toughness version in Monster Manual V, p. 205]
In reference to Dwarf’s comment found here
Figured it was time to make it a House Rule.