My clients often explain to me how they set a boundary. They tell me something like, "I set a boundary. I told him he has to stop putting me down in public," or "I set a boundary. I told her she has to be on time from now on," or "I set a boundary. I told him he has to stop being critical of me."
This is not a boundary. A boundary is not about telling another person what to do. It is about telling another person what YOU will do in the face of the other's continued unkind or undesirable behavior. While it is hard for most people to accept, we cannot control another's behavior. What we can control is our own response in the face of others' behavior.
A boundary is about telling your truth and taking action on it. For example:
"I'm no longer willing to be with you in public when you put me down. The next time you do that, I will announce to everyone that I'm unwilling to be put down by you any more. Then I will leave and take the car or a cab home."
"I'm no longer willing to be late to events because of you being late. The next time you are late, I will leave without you. If you continue to be late, then I will just plan on taking separate cars."
"Your constant criticisms feel awful to me. From now on, when you are critical, I will tell you that it feels awful and leave the room."
Then, of course, you have to take the action you have said you would take. If you do not take the action, then what you have said is a manipulation rather than a truth. A boundary means nothing until you are willing to take the action.
The tricky part of this has to do with your intent. If you intent is to control the other person rather than take loving care of yourself, then your statement and action is just another form of control. If your desire is to take responsibility for yourself, then your tone of voice will be calm and matter-of-fact—just letting the other person know what you will be doing or are doing. If your desire is to control the other person, then your tone of voice will be angry, blaming and accusing, and your energy will be hard and closed.
We cannot hide our intent—it will always come through in our energy and our tone of voice. Whatever means you use to try to mask an intent to control, the other will always pick up on it and probably react to it with his or her own controlling behavior.
You are coming from a place of personal power when your intent is to take loving care of yourself rather than control the other. Since you cannot ultimately control another, trying to will leave you feeling frustrated and powerless.