When my former boyfriend discovered that I had cheated on him, I felt physically sick with guilt, despair, and grief. But I also had plenty of excuses as to why I did it.

After I moved thousands of miles away for a job, we struggled to adjust to a long-distance relationship. I felt neglected, lonely, and unable to communicate what I needed via Skype. When I met someone new and exciting, I told myself we were just friends. And then we weren’t.

During our first visit in nearly a year, I forgot to log out of my Facebook on my partner’s laptop. He read my messages, and the life we’d built together exploded. Of course, it was all my fault-I’d planted the bomb and somehow hoped he’d never find it. Many painful, hours-long conversations followed, as did an attempt at an open relationship. But we couldn’t recover.

A few years later, I got a taste of my own medicine when a new partner cheated on me. I completely lost it, and despite my need to ask how he could hurt me like that over and over again, none of his explanations mattered. In my mind, he was bad, cheating was bad, and it was that simple. Pretty hypocritical, right? Unfortunately, I’m not alone.

Cheating can destroy a marriage, shatter your ability to trust future partners, hurt your kids, and even lead to depression, anxiety, and post-traumatic stress disorder (PTSD). The vast majority of adults agree that it’s wrong, but anywhere from 39 to 52% of us may experience infidelity at some point in our lives.

Why do people cheat?

“There’s a multitude of reasons why people cheat,” says Kenneth Paul Rosenberg, M.D., a psychiatrist and author of Infidelity: Why Men and Women Cheat. According to a 2017 article published in the Journal of Sex Research, explanations for infidelity often dip into three main categories: personal problems, beliefs, or characteristics; issues with your partner or the relationship as a whole; and situational factors like easy access to dating websites, long business trips, or liquid courage.

To further complicate things, sometimes what “counts” as cheating to you may be radically different from what your partner sees as okay versus definitely not okay. Research shows our definitions of infidelity can range vastly from having a celebrity crush or watching porn on the conservative side to only in-person sex acts on the more liberal side.

Although sexual relationships are often considered the worst of betrayals, Dr. Rosenberg says it’s important not to underrate emotional affairs, which can be just as devastating.

If you’re here, you’re probably trying to muut understand why you, your partner, or someone you care about cheated. There may be no single reason why, and it’s often difficult to get a satisfying answer out of someone who has mastered the habit of lying to you or feels deeply ashamed and confused.

But to give you some insight, we asked real people to explain why they cheated-and asked relationship experts to weigh in on the reasoning, plus how you can begin to sort out what comes next after infidelity.

1. The relationship wasn’t fulfilling anymore.

I cheated because I was really dissatisfied with our relationship and didn’t feel seen or understood by my partner. I confessed immediately afterwards, and today, my ex remains one of my oldest friends. Looking back, I wish I’d had the emotional intelligence at the time to tell him how I felt or break up with him. -Taylor C., 23*

One common reason for cheating is that the partnership isn’t satisfying, says Ashley E. Thompson, Ph.D., an associate psychology professor who researches infidelity at the University of Minnesota in Duluth. If you’ve grown distant, don’t have anything to talk about, or can’t remember the last time you had sex, you or your partner may end up looking for connections outside of the relationship rather than trying to fix problems at home.