If you train your slave properly, you can expect to see this kind of pride on it's face after an intense session of abuse because it's position in life is so thoroughly reinforced that it finds it's purpose in serving and accepting daily punishment.
Darling Emma, I am surging along with your life blood, coursing through the secret places of your body. I wish to escape from you but I am harried from place to place in my thots. I cannot escape from the rhythmic spurt of your love juice.