Being negative doesn't only kill your creative juices but actually can lead to a deadly disease! According to researchers of King's College London constant reliving of past mistakes or worrying about terrible things that can happen in future can alter your brain and potentially lead to Alzheimer's disease.
Repetitive negative thinking puts your body in a state of stress increases production of stress hormone cortisol, and activates certain regions of brain that are implicated in Alzheimer's disease, says study author Natalie Marchant, Ph.D.
Researchers say that negative thinking alone elevates the odds of getting a disease even without depression and anxiety.
So you better be an optimist and leave past in a past(just learn the lesson and move on!).