Whenever you get knocked down, you spring right back up.
Benefit: The first time that you are knocked prone each turn, you may stand up as an immediate action. Additionally, any time you attempt to get up from prone you may make an Acrobatics check. The DC for this check is equal to 5 + the CMD of any opponent that would make an attack of opportunity against you for standing up. If the check succeeds, you do not provoke an attack of opportunity from that creature.