One of the eight reasons why some people self harm is because of a self hatred or as a form of self punishment. As a result of childhood experiences some people end up with a self hatred or with a sense of self loathing. This may be because they were told precisely that. They were told they were useless, worthless, not wanted, hated and loathed by the parent figures.
In other circumstances the child may have been physically and sexually abused. When this happens sometimes the child has faulty thinking and believes the reason why they were abused is because there is something wrong with them. It was because of their inherent badness that the parents physically abused them. The child thinks that it is their fault and thus a sense of self loathing and hatred can evolve in their perception of self.
If a person has a basic sense of self hatred that does not mean they are going to be suicidal. A person will be suicidal if they have made the suicide decision and thus see suicide as a viable solution to their problems. There are plenty of people who have a basic self dislike who do not see suicide as such a solution.
Those who do have a very low self perception will self harm in some form but maybe not in the usual sense of the word. That is they will not self harm by cutting, burning or stabbing self but will self harm by the lifestyle they live. For instance a woman may prostitute herself at least partially because she hates herself. This could be seen as a type of self harm in terms of the life style she lives.
Any person who has a sense of self loathing will somehow live a life style where they treat self very badly either physically and/or psychologically. For instance the drug addict type of drug user can be taking drugs in such a way that it amounts to physical self harm. Such as with intravenous drug use where they share dirty needles with high risk others and so that their veins eventually become essentially mutilated.
Most drug addicts also hate themselves for being an addict. They know society views a junkie as being at the lowest level of society. They are seen at least by some as the useless crap at the bottom of the pile and often view themselves in a similar light. This can amount to psychological self harm. Thus the drug addict may hate self and that is expressed by self harming physically and psychologically.
Despite this there are a group of self harmers such as ‘cutters’ who harm self as an expression of their self hatred and self loathing. They cut self as an expression of these thoughts and feelings about self. Some self harmers will talk of bloodletting as a way to getting rid of some of their badness. As the blood flows out they see their inherent badness also flowing out.