Considering the dejected mood that typically accompanies depression, people are generally negative about themselves and their situation in life.
However, this particular symptom, in addition to other symptoms in depression, seem to place all of its energy on the pummeling of the self.
The person may feel like they are not good at anything or not good people at all. As with a lot of the features in depression, the actual evidence supporting these self-disliking/defeating attitudes could be completely arbitrary. No matter, they produce negative emotions that contribute to the illness.
This symptom, along with a few others, exemplify the distinction of depression and other illnesses in that, the illness in itself get the person to turn on themselves. That is, a direct assault on who they are as well as their own worth as people.
Person feels disappointed in themselves.
Persons disliking becomes disgust.
The person begins to hate themselves. Even wishing death after a simple overview of who they are.