There are many different ways to define dark psychology. Dark Psychology is the art and science of manipulation and mind control. Psychology, in general, seeks to study and understand human behavior. It is focused on our thoughts, actions, and the way we interact with each other. Dark psychology, however, just focuses on the kinds of thoughts and actions that are predatory in nature. Dark psychology examines the tactics used by malicious people to motivate, persuade, manipulate, or coerce others into acting in ways that are beneficial to themselves, and potentially detrimental to the other person. – J Mind.
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Dark “Personal  Manipulation” Tactics is the intentional enforcing upon ourselves an acceptance of “darkness” (evil/bad) in our character due to weaknesses, something bad but we want to participate in, so we defend it in our mind and to others. These weaknesses, although obviously bad/evil, we defend our right to participate in them, especially in our own minds, and we often proudly and loudly demand that other people believe that our “darkness” is light.
– James Martin Sandbrook.
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Piggy-Back Dark Manipulation Tactics are the passing on of an “Accepted Darkness” on to another person. This could be from narcissist manipulator to victim. From narcissist parents to their children. Or from school friend (an introduction to casual sex or drug abuse) to another school friend. Criminals to their children. Gang Members to their children. Or from parent to child, such as bad habits, sex abuse, violence, emotional abuse, and the child grows to an adult who see’s no wrong in the darkness that they were taught as a child.
In history having a Problem, or an Evil Spirit, having an Issue was having a Monkey on your Back, once the monkey is removed the problem is gone.  When the parent has a darkness in their life that is accepted as a norm then that was called a Dark/Evil Monkey on that parents back of which that parent passes on to their child so that child now has a Evil-Monkey on his or her back as well. The child goes through life with that Evil (manipulative)-Monkey on his or her back riding-them piggy-back causing all sorts of issues, darkness and suffering to all that know this person with the Monkey on their back.
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When a narcissist manipulator uses tactics to manipulate a person they are controlling that person and manipulating the victims mind.
Personal Manipulation is the manipulating our own mind to accept, agree with and to become something that is a “darkness”, a part of society that causes harm to ourselves and others but we refuse to accept that in favour of what “we want to believe”.
Any proof or evidence that appears before us showing us that what we are doing or have accepted as a belief is wrong, is very quickly (and often proudly) denied because to face the truth is too uncomfortable, too shocking, so it is very quickly denied and an even stronger effort by our own mind to fool ourselves is made with often fierce mental-force to demand of our own self to stand by old toxic and dark beliefs to remain loyal to those who taught us darkness in the first place.
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“Sometimes people hold a core belief that is very strong. When they are
presented with evidence that works against that belief, the new
evidence cannot be accepted. It would create a feeling that is
extremely uncomfortable, called cognitive dissonance. And because it
is so important to protect the core belief, they will rationalize,
ignore and even deny anything that doesn’t fit in with the core belief.”

― Frantz Fanon