Neuro-linguistic Programming (NLP) shows you that the meaning you attribute to an experience is dependent on the way you unconsciously code the pictures, sounds, and feelings associated with that experience.
You can discharge the negative impact of a past event by changing the coding of the mental pictures, sounds, and feelings that are evoked when you think about it. For example, to change its effect, you can make pictures brighter or less colourful and sounds louder or more muted. If you become conscious of where a particular feeling is located in your body, you can move it somewhere else.