Lucatiel's anguish is compelling. It's never stated in the game just how your character is affected by the curse- but you felt strongly enough to cast yourself into a raging whirlpool.
My guess is that the physical rot of Hollowing is accompanied by mental degradation, failures of memory, loss of identity- those max HP you lose, those aren't about your decrepit flesh. As we see later in the game, hollows can become monstrously powerful. It's representing the diminution of will :-(
