These behaviors are very addictive. To quote Rabbi Avraham J. Twerski in a recent talk:
You have no idea as to what category of people have fallen victim to internet pornography. We would not think that these type of people would be capable of it. Hopefully nobody who’s a Yirei Shamayim is going to go look for that kind of trash and that kind of filth. However, it is perfectly possible that while monkeying around with the internet, you hit a button and there’s a pop-up of a pornography scene. You weren’t looking for it, but it happened. You have exactly 3/10ths of a second to turn it off. And if you avoid it for 4/10ths of a second, you may become addicted. That’s how severe it is. It's one of the most powerful addictions. Day after day after day - I get letters and calls from people who say, "what can I do to save myself?
If we find that we keep falling into inappropriate behaviors that go against our conscience and better judgment, and we have tried countless times to stop in the past but always seem to fall back to them in the end, then we are probably struggling with an addiction. As Rabbi Avraham J. Twerski says:
The ultimate distinction between man and animals is not that man is more intelligent, but that animals are creatures that have no choice over their behavior. They must do whatever their bodies demand. They cannot choose what they should do. Man has the ability of self-control, to choose one's behavior, even in defiance of physical urges. If a person loses one's ability to choose and is dominated by urges one cannot control, one is indeed an addict.
We may have tried to do Teshuvah many times in the past, but the standard model of Teshuva (Azivas Hachet, Charata and Kabbala al Haba) doesn't always work for us very well anymore. Addiction is a type of disease, and our Sages understood the nature of addiction, as the Gemara (Avodah Zara 17a) says in relation to the story of “Ben Durdaya” who had been with every prostitute in the world, “Kivan dehava adik be’aveira tuvah, ki’minus dami – since he was entrenched in the sins a lot, it was similar to heresy”. Rabbi Twerski points out how the word “adik” is very similar to the word “addict”. Also, Rebbe Asi said: "The Yetzer Harah in the beginning is compared to a strand of a spider web, and in the end like a rope that is used to tie cattle". Our Sages recognized that once a person repeats a particular sin a number of times "it becomes to him as if it is permitted". Even more so, in this area where our Sages have said: "The more it is fed, the hungrier it gets". Therefore, the standard Teshuvah techniques are not usually sufficient in our case anymore. Once these behaviors have progressed to addictive levels, will power alone is rarely effective in dealing with them and it is no longer just a "Yetzer Hara" issue. Addiction is a spiritual and psychological disease. It is important to understand that we are not simply dealing with a “stronger than usual” Yetzer Hara, and we are not just “weak-willed” people who can’t control ourselves. The Sefer haChinuch on the Mitzva 387 “Do not stray after your heart and eyes”, compares lust to alcohol addiction, describing how the more it is fed, the more it wants and the harder it is to break free of it. The nature of the addiction is analogous to someone standing on the railroad tracks while he watches the train bearing down on him, and yet he can't move himself out of the way. And as Rabbi Twerski puts it in his book "Addictive Thinking": We place our hands on the stove, get burned, and yet we feel compelled to do it again.
How do these behaviors lead to addiction? It’s simple neuroscience. Just like with any pleasure, the pleasure sensory is stimulated in the brain. Whether its cocaine, alcohol, or pleasure one might get from inappropriate scenes viewed during a movie, the serotonin levels spike and the dopaminergic pleasure pathways are activated in the standard "addiction" pattern. As a matter of fact, these behaviors have been shown to be MORE powerfully addictive than most drugs, in one study. It's not a big wonder why that would be. It's an intense pleasure stimulation, even more direct than a hard drug. And upon repeated exposure to certain types of stimulation, one tends to seek out even more perverse and intense stimulation, leading to that vicious self-destructive cycle that is typical of addictions. What was enough yesterday to achieve a ‘high’, is no longer enough today to achieve the same effect.