(CNN) -- Anthony Weiner resigned from the U.S. House of Representatives in 2011 after admitting to sending lewd images to multiple women. But it seems that getting caught wasn't enough to stop him from repeating his mistakes.
The New York mayoral candidate admitted at a news conference Tuesday that he was exchanging sexually explicit messages and photographs with a young woman last summer.
"I wasn't surprised that there was more stuff that came out," said Ian Kerner, a sexuality counselor in New York who has not spoken with or treated Weiner. "I was surprised that more events, more sexting, seemed to go on for ... close to a year afterward. That was shocking."
When we see someone like Weiner -- who has everything to lose -- continue to engage in this self-destructive behavior, we assume there is a deeper psychological issue at play, Kerner says. But the underlying causes may be more common than we'd like to think.
"Self-destructive behavior" can apply to almost anything, Kerner says. How many times have you eaten more than you know you should? Lied to cover up a missed deadline? Gotten into a fight over something stupid? And how many times have you done the same thing again, wondering why you didn't learn your lesson the last time?
We often use self-destructive behaviors as coping mechanisms, Kerner says. Some people dive into a jumbo-sized bag of potato chips when they're stressed; some chain smoke; others indulge in sexual behaviors.
"Everyone can relate to having stress and anxiety," Kerner said. "In that state of emotion, anxiety, you lose your ability to control your impulses."
But why would someone have the impulse to send a photo of their junk to a stranger on the Internet?
"Honestly, in many cases, you don't need to explain why fantasies are popular or exist. They simply do exist," he said. This one is commonly referred to as voyeurism. "People in the privacy of their own bedrooms love to share exhibitionist fantasies: watching somebody, being watched."
In this case, Weiner is showing signs of something psychologists like to call "situational narcissism," Kerner says. It's the same behavior we see from celebrities or people in power who think they are above the law or the rules other people follow.
Clearly, Weiner knows that what he's doing could lead to trouble: He's been busted before and has seen the consequences. But that might just make sexting even more exciting, Kerner says. It's comparable to the way drug addicts keep escalating the drugs that they use; they need more and more to get the same high. The bigger the risk, the bigger the reward.
"Sex addict" is often the first thing people think when they hear about an incident like Weiner's, says Lawrence Josephs, a professor of psychology and infidelity expert at Adelphi University in New York who also has not spoken with or treated Weiner.
(It's important to note that the official psychiatric handbook, the Diagnostic and Statistical Manual of Mental Disorders, doesn't include sexual addiction. It discusses hypersexuality but does not consider it an official clinical diagnosis.)
Also called compulsive sexual behavior, some experts say, sex addiction is like a gambling addiction or alcoholism. Addiction in this context means it's a behavior that you cannot stop, even if you damage relationships or suffer other negative consequences. That could mean extensively using pornography, having affairs or masturbating excessively, to the point where it interferes with your daily life.
"Most people do not want to betray the trust of a loved one, and even fewer people would want their betrayals to become a chronic pattern, which destroys the cohesiveness of their family," writes Alexandra Katehakis, founder and clinical director of the Center for Healthy Sex in Los Angeles, for Psychology Today.
"They substitute unhealthy relationships for healthy ones in search of the intensity that sex gives them. They opt for temporary pleasure rather than the deeper qualities of intimate relationships because they can't help themselves."
Addicts are never fully "recovered," Josephs said. Anyone who engages in a compulsive behavior, he says, may be able to stop for a week or month before experiencing withdrawals. But even a year into recovery, they are still at risk for a relapse.
"It's also hard to know when people really stop," Josephs noted. "People claim they're abstaining, but that (may be) a lie. You don't really know."
And therein lies the problem Weiner will most likely face in running for mayor.
When a couple faces infidelity, Josephs says, the trust in the relationship has to be rebuilt. If you've been caught lying and then lying about lying, what you say loses meaning. Actions will speak louder than words in the coming months for Weiner, he says.
"It's not enough for somebody to say, 'Trust me, I haven't done it anymore,' " Josephs said. "You have to see it: real behavior change."
Weiner's wife, Huma Abedin, says she has forgiven her husband for his mistakes. At the news conference, the couple said they were moving forward.
"Anthony has always been a smart, caring, and dedicated person, and while he's the same public servant who wants what's best for the people he represents, he is now something else -- a better man," Abedin wrote in Harper's Bazaar magazine. "New Yorkers will have to decide for themselves whether or not to give him a second chance."
CNN's Elizabeth Landau contributed to this story.