Many people define themselves by their past. If you had physical, emotional, or sexual abuse in the past you are angry, depressed, anxious, resentful, mistrusting of people and can not do anything about it, it's just the way it is. However, more people now are discovering that you choose how you think and feel everything that happened.
The first thing to realize is that you can choose how you think and what you think about. If you are thinking about a past wrong that happened to you, realize that you do not have to dwell on it. Most people dwell on problems and difficulties because they believe that they have to keep thinking about the problems until they reach a resolution. Consequentially, they spend their whole day feeling worried, angry or depressed and often lose sleep as they continue to dwell on the problems.
When you consider what thinking is, it's problem solving. The negative side to that is that if you do not make a conscious effort to control your thinking, you will tend to think about your problems. The good thing is that you can decide what you are going to think about. You could be angry thinking about a time when you withstood abuse or misunderstood by parents, or a lover, or you could choose to think about a recent vacation your went on, or a recent accomplishment. You can feel overwhelmed thinking about how you failed out of college before and you are back in and having a test, or you could think about setting aside study time and choose to focus on the material. You could get depressed thinking about what you used to have, or you can think about what you have now and what you could now do to acquire more of what you used to have.
You may have observed from the previous examples that you can use thinking as problem solving for good and not to make yourself unhappy. Imagine if you think of every past experience as something to learn from. If you were repeatedly criticized in the past you can now be easier on yourself. If you were physically or sexually aborted in the past you now can plan to protect yourself. If you do not trust people because of past abuse, you can learn to discriminate between people who you trust and those you do not. Therapy is a big help with this.
Once you arrive at a solution for the problem memory you no longer have to dwell on it. If you start thinking of the memory you can consciously choose to think about something that is more pleasant. You get to choose!