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.
ANNOUNCEMENT - Sold my second subject of my latest auction. Subject Stacy has been sold to u/Evilcat38 for 20g of gold. Subject Crystal is still in talks. Subjects Alexis and Elle have yet to receive an offer. Follow link in comments to see auction post.