People who were abused in their families of origin may practice the same abusive behavior towards themselves. They may also pass it on to their children. This creates a sick, and sometimes fatal, cycle of abuse that repeats itself generation after generation.
We tend to do what we know and what we know if what we were taught in our families. If we were taught abuse we tend to grow up to abuse others or to pick out people who will abuse us. If we were raised with lots of verbal abuse our Self Talk as an adult may be laden with this exact words and phrases. People who have been labled "losers" by their family may actually sabotage efforts which result in success so they perpetually end up losing. This is what therapists call a "Self Fulfilling Prophesy". If we tell someone they are losers to the point they grow up to call themselves a loser they will often end up being just that.
People who were sexually molested as children may engage in prostition, lap dancing or other sexual behaviors in an attempt to replicate the abuse. They may engage in superficial relationships which only involve sex without intimacy. They may actively purpose sexual sadism or masochism. They may be obsessed with having sex, i.e. "sex addiction" or may develop a heavy dependence on porn. In this way they continue to keep themselves and others in a sexual, de-humanized role.
If the abuse was in the form of alcoholism, the adult child of an alcoholic may become an alcoholic themselves or marry an alcohol in attempt to rescue him or her. If the parent's alcoholism was combined with verbal messages that the child was "no good" or would "never amount to anything" alcohol may be used to sabotage efforts to succeed.
I once worked with a man, Joe, who was a heavy alcoholic and worked in the salvage industry. I was told he was so heavily addicted to alcohol his wife had to administer an alcohol enema every morning in order for him to function. (A true enabler.) The salvage business is either feast or famine. If a train crashed yesterday it might be a feast. If nothing needs to be salvaged - famine. When Joe hit the jackpot he would walk away with a huge roll of cash stashed in his boot. He went straight to the bar with his other "friends" who would quickly relieve him of his cash. One Friday Joe stopped by the office before going to the bar with his huge roll of money. He was already on his way to being full out drunk. His real friends talked him out of the money and put it in the safe. He went to the bar, stayed drunk all weekend and came in on Monday morning quite happy. We were so proud of ourselves for having saved Joe from himself and quickly ran to the safe to retrieve his money. His smile dropped and he looked at us with suspicion. We could not understand why he was not happy. He immediately took the roll of money to the bar and drank until his "friends" had relieved him of it.
With people battling eating disorders you can often see this same pattern. They may lose huge amounts of weight, but then gain it back. Why? It is not always the case, but sometimes being thin is scary, especially if they have put off living their lives until they were thin. "I'll apply for a new job when I'm thin." "I'll try my hand at having a relationship again when I'm thin." "I'll leave this messed up relationship I'm in when I'm thin." Getting thin means they will have to act on these promises they have made to themselves - and that can be very scary. Hooking back up with friends you know will take you to the all-you-can-eat buffet, who notoriously overeat and who encourage you to overeat is a sure fire way of sabotaging a diet.
Look back on your own behaviors and those of your parents. Do you see any patterns? Completing a genogram can be very helpful in identifying patterns in your family and predicting patterns you might adopt. Identifying maladaptive patterns can be an important first step in stopping them; not only in yourself but in your children. See also, "The Voices in Your Head: Tuning in to Your Own Self Talk" for ideas about identifying and changing your self talk.