You just have to stand your ground and protect your personal boundaries. - Flipper
Very true Mr. Flipper. That's how I managed to end things with my ex-husband. Controlling people rely on getting you to change your mind. Standing your ground and sticking to your guns takes away their power.
Be aware of the little things within any kind of relationship that gives the other person control. Things like never letting you choose which film to watch, dictating what you should wear/listen to etc. A controlling person will often attack these areas of your life first. We can see how the WTBT$ does this, but within a personal relationship the controlling person may be more subtle, perhaps seeming to jokingly mock your personal tastes and suggesting that theirs are better, especially in front of others where you will feel pressure to conform. If this has happened to you, then I suggest working on these areas first to regain control. Then hopefully the other person will either respect your other boundaries too, or you will feel more confident in standing your ground on bigger issues.
((Hugs)) I have been there. I lost many friends, personal possessions (clothing ripped from my body, items smashed up in rage etc) and had to rediscover who I am. If the use of violent force is involved in trying to control you then please make arrangements to GET THE HELL OUT!