Instinct.

Ichigo, do you know what's the difference between a king and his horse?


I don't mean the kiddy shit like "One's a person and the other's an animal" or "one has two legs and the other has four" ! Why is it that one becomes a king and controls the battle, while other becomes a horse and carries the king!? There's only one answer: INSTINCT! Deep, deep within our bodies lies the honed instinct to kill, to slaughter! You don't have those pure, basic instincts! You fight with your brain. You try to defeat your opponents with logic, and it doesn't seem to work! You're trying to kill them with a sheathed sword! That's why you suck Ichigo!

Shirosaki - Bleach.