It's been said, "If you love something, set it free." If you keep someone around just to keep using them, why be surprised when they are hell-bent to break the leash?
Tightening your chokehold on them won't do anything beneficial; you'll just end up with a dead pet on your hands.
Be sure not to treat humans like servants, or pets. Even animals have free will to a certain extent. Shouldn't a human be allowed that trait as well?