Image: Rebel Wolves / Bandai NamcoOfficial screenshot from Rebel Wolves / Bandai Namco.
Balanced Diet is a progression achievement for drinking blood ten times. It comes quickly as long as you feed when you are actually hurt.
Drink blood from ten targets. Animals, humans and monsters all count, so mix it up as you go.
Feed when your health bar is down. A drink at full health may not count, so take a few hits first if you are farming it. Feeding also raises Corruption, which you need for Creature of the Night.