lake Kingdom Hearts 2 boss help....I can't kill this guy!Please help!?

ok, im in organization 13's stronghold (The Place That Never Was). I'm trying to kill number || named Xigbar. I got very close one time he had about half of his last health bar left, but what gets me every time I try, is when the place changes and you are standing on a square platform without holes and he has blue kind of glowing around him and he says like try this or something like that, and then he starts shooting these millions of blue lasers EVERYWHERE and you can't block them because they all just keep hitting you and they are coming and going from everywhere. All I can do is just sit there and take the beating. I have a pretty great health bar but when he does that I'm just losing all my health and then I die! If it wasn't for this attack I think I could actually kill him. But it just isn't happening! Please help me!! Thanks in advance!:)there