You can shed negative levels with an act of will.
Prerequisites: Endurance, Enduring Life.
Benefit: Once per round as a standard action, you can attempt to remove a negative level from yourself by attempting a Will save (DC 10 + ½ attacker’s HD + attacker’s Charisma modifier). If the saving throw succeeds, the negative level goes away. You make a separate saving throw for each negative level you have gained. If the save fails, you retain the negative level, but you can try again next round to remove it.
Source: Libris Mortis, page 28.