This is not my writing but from DailyOM.
Our past experiences, can and do, influence our emotional reactions and responses to present events.
Our experiences color everything. The events of the past can have a profound effect on how we see our lives now and what we choose to believe about our world. Our past experiences can also influence our emotional reactions and responses to present events. Each of us reacts to stimulus based on what we have learned in life. There is no right or wrong to it; it is simply the result of past experience. Later, when our strong feelings have passed, we may be surprised at our reactions. Yet when we face a similar situation, again our reactions may be the same. When we understand those experiences, we can come that much closer to understanding our reactions and consciously change them.
Between stimulus and reaction exists a fleeting moment of thought. Often, that thought is based on something that has happened to you in the past. When presented with a similar situation later on, your natural impulse is to unconsciously regard it in a similar light. For example, if you survived a traumatic automobile accident as a youngster, the first thing you might feel upon witnessing even a minor collision between vehicles may be intense panic. If you harbor unpleasant associations with death from a past experience, you may find yourself unable to think about death as a gentle release or the next step toward a new kind of existence. You can, however, minimize the intensity of your reactions by identifying the momentary thought that inspires your reaction. Then, next time, replace that thought with a more positive one.
Modifying your reaction by modifying your thoughts is difficult, but it can help you to see and experience formerly unpleasant situations in a whole new light. It allows you to stop reacting unconsciously. Learning the reason of your reactions may also help you put aside a negative reaction long enough to respond in more positive and empowered ways. Your reactions and responses then become about what’s happening in the present moment rather than about the past. As time passes, your negative thoughts may lose strength, leaving only your positive thoughts to inform your healthy reactions.