Your sense of power, part of your self-esteem, depends upon your satisfaction with your own performance. And if you are trying to control someone else, you begin to think of what they do as part of your own performance. That is, just as there are boundries or borders between countries, there are boundries between people. These boundries can't really be crossed. Type A's who are likely to have heart attacks are those who are frustrated, angry and hostile from trying to control the behavior of others or trying to control other things that are not within their power.
Control means choice.
Self-Control is of emotions, thoughts, body and behavior. Control of emotions, rather than elmination of emotion, means being able to choose emotional responses. Control of thought means being able to choose when to think, what to think about, how to think about it and to not think about something. Control of behavior means being able to choose everything you do within the limitations of time, place and conditions. That is to say, the behaviors available to be chosen are limited by such factors as whether it is night or day, whether you are at sea or in the mountains, how energetic or fatigued you are, and so forth.