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It may be possible to change negative emotions to positive emotions by doing the opposite of what you feel like doing. This skill is called “Opposite to Emotion Action.”
For example, if we feel sad, the urge generally is to isolate. Therefore the opposite action is to get active (get up, take a shower, call a friend, etc.) This skill requires some effort initially. However, positive results are usually noticed within minutes. It often helps to remind ourselves how good we will feel once we start doing something positive — like the last time we did that positive activity.
Another example might be that it is difficult to get off the couch and go to the gym. However, if we push ourselves over that initial hump, we feel good while exercising and we feel proud of ourselves for going. We use the tool of visualizing how good we feel when we exercise as motivation to go to the gym.