"the reality of our life is not very nice or jolly once we get to certain age. we view life that it's not like what we thought it was. so we get to see our dreams/hopes crushed by things that happen. we just have to realize at the point that life we're living in is harsh reality.
so we have to let go of our reality that was only a illusion of what we really thought was our own cheerful life. then the harsh reality hammers into us really hard by events that happened to us." ~ to Dovahbrony on Korra Subject.