引用:

Alongside your item selections and ammo count are your health and stamina bars, and it's here where From Software has made another tweak, in order to encourage a more aggressive, less defensive style of play. That tweak is called the regain system. As you receive damage from enemies, your health goes down. If you played defensively and backed off, that health would be lost forever. But in Bloodborne, you can actually claw that health back by launching a well-timed counter attack. A yellow bar that appears beside an enemy after the land a hit works as a timer: get in a counter attack before it disappears and your health is restored.