Past trauma is often the cause of over reacting to a situation in the present.  First, is to identify when you are over reacting.
     Are you being triggered by words or emotions that are being aimed at you or are you projecting your own thoughts and feelings into the situation? Perhaps you left home this morning with unresolved emotions about your life and when you get to work everything there triggers your own questions about what you are doing with your life.  It is nothing personal with any of the people at work. You may not want to work there anymore and nothing will make that better except quitting.  Then you have to deal with not having a job. Then you are frustrated by why you didn't stay in college and get a degree so you would have a job that you liked etc. That is a big issue to deal with not the seeming little problem with someone at work who pisses you off.
     Some people have a problem with authority because of a parent telling them what to do when young and it brought up resistance. They didn't feel they were making up their own mind and will so they bring that into the present and feel that way toward anyone who tells them what to do.  The prisons are full of them.  Parents are supposed to guide and protect their children and that means telling them what they can and cannot do.  Regardless of how imperfect your parents were, it might be time to realize they were doing their best to protect you and keep you safe. If they did harm to you, realize that you are now grown up and it is your job and responsibility to keep safe and learn what behavior is good for in your life.
       No matter what happens to you, you have a choice as to how you respond. You can end the reactions caused from past trauma. Realize current situations are triggering memories of something that made you feel the same way. The key is to figure out how you are feeling.  This can be hard because unpleasant memories are often buried in the unconscious, filed under "too painful to deal with." If you can find the courage to look under that 'rock of denial' then you may be able to find the origin of what is triggering you. Most likely you are no longer a child so you are more equipped to deal with the past childhood memory. An adult has way more experience in coping with bullies, disappointment, unfairness and not getting one's way. You are an adult, responsible for yourself. You choose what happens to you and how you respond to what happens once you become more aware of your total experience. This is something that can be learned by observing the four aspects in PEMS and going deeper with time. When a person becomes aware, they are more able to choose their experience. Until that time one is at the mercy of reactionary patterns acting out from the unconscious.  We all want to be happy and heal wounds from the past. Creating a safe space for your emotions to speak through writing will reveal what has been hiding causing you pain and interfering with your present situation.