Someone who needs to be controlling in a relationship is someone who is not secure in how their significant other feels about them. Maybe they have been hurt before and trust is an issue, but there are classic signs that signify someone is being controlling.
The first sign is when the person makes suggestions that are more like demands. You change your hairstyle without telling them first and their comment is something like "you will let it grow out, won't you?". Trying to control how you look is how some people control a relationship. If they can control the persons actions, they can be in control of the relationship.
Another classic sign of controlling a relationship is when the person snoops into your private stuff. Whether it is a drawer that you keep personal items in or hacking into your email, they have to make sure that they know everything about you. They do not trust you and need to make sure that they know all your secrets.It is disturbing to feel violated by someone you care about.
For someone who is very outgoing, being in a relationship with someone controlling will eventually put an end to your night out with friends. If you attempt to fight back and demand your time alone with friends, it will cause much fighting and the controller will do everything to wear you down. This is where some relationships should end but too many continue with the controlling person getting their way.
When a son or daughter marries a controlling person the whole family usually suffers from it. The controlling spouse will find reasons to keep their spouse from his/her family. It may happen slowly but eventually it will happen. If you have children it can really get ugly. A controlling person feels threatened by grandparents and will do everything to discourage the grandparent/grandchildren relationship.
If you have interests that your partner does not share with you, those may be a thing of the past also. If the controlling person sees no need for you to have activities that they cannot enjoy, they will use pressure of every kind to get you to give up what you used to love. You may even find that you are now participating in hobbies that you really dislike all at the urging of your controlling other.
The controlling person has you brainwashed to think that you are the one with issues. You may feel guilty about how you feel, but that only shows how good they are at making you doubt yourself. Being in a controlling relationship can be similar to an abusive relationship.
A controlling relationship is certainly not a healthy one. Even if you try to please the controller, you can never win. They are too insecure for anyone to make them happy. They need to be happy themselves and they have trust issues that need to be resolved before they can be part of a healthy relationship. The sad part is that many people who feel the need to control a relationship do not change. Even if the other party wises up and gets away from them, they will just go on to their next victim.