Dr. Jacqueline B. Sallade offers ideas for maintaining your mental health.
Children learn conscience by example, not by punishment, not be lenience, not by lectures. They see parents doing what's right, not what's easy. They see consistency, not reactions which come naturally at the moment. Sometimes, people explain what they're thinking and doing, mostly they just refrain from acting badly in times of temptation and act morally or not at all (which can be a valid choice, too).
Of course, little children do the wrong thing selfishly and naturally, like hitting, taunting taking things and worse. They develop other options best when helped to correct that behavior. Reinforced positively with praise and love for kindness, helping others, and treating people well, they develop a sense of self-respect and a reputation in the family and beyond as "nice" or "good."
However, when major attention and the setting of necessary limits, which enhances a sense of security, comes from "acting out," children come to think of themselves as "bad," and they live up to that reputation. Their self-respect is distorted by oppositional behavior, at least, and a criminal-like bravado, at worst. Getting away with more and more becomes de rigeur, since they haven't integrated self-control as a sturdy part of their psychological vocabulary. This pattern occurs in conditions of wealth and in poverty, often including drugs.
Are these children, now drop-outs from respectable society, even if narcissistically pleasant on the surface, salvageable? Often yes, but not without a lot of hard work. Usually, some drama needs to initiate the need for change, like arrest, illness, death of a friend or relative, or, more positively, falling in love. Then, positive role models must show up. A variety of experiences can provide perspective, from deep psychotherapy with imagery and cognitive training to wilderness camp. In some cases, religion plays a role, but that possibility can be blinding, as well, impairing a sense of free will and choice.
Every case is different. Personalities, life experiences, and intellectual strengths and weaknesses come in so many permutations and combinations. But, I have seen change happen, with some motivation and the right influences. People aren't totally static. While past behavior usually predicts future behavior, that's not the case with heavy, full strength intervention at the proper time.