Mood-Congruent Behavior
Mood dependent retrieval is a label given to the human tendency to be able to better retrieve memories when in the same frame of mind as when the memories were initially encoded. This is why that when we are in a sad or angry mood it becomes so easy to remember other times when you were sad or angry, and what caused those moods and spiral down further into those moods. Likewise, when in a happy mood it is easy to remember and reminisce about other happy times. Because of this tendency to "dwell" on past events, especially the unhappy events, it is healthy to recognize this tendency and to learn to divert attention rather than spiraling into bad moods and memories.