Rumination

"Why do I always feel so sad?"
"I always think back to that event in the past where I felt humiliated and defeated"

Rumination is characterized by the presence of recurring thoughts than events with negative valence. It mainly concerns past events or negative emotions of the present. These thoughts are associated with feelings of failure, loss, and to a state of 'markedly depressed mood.

This kind of thinking tends to aggravate the negative mood and impairs memory and concentration of people who suffer from mood disorders.