I’ve noticed that sometimes when I comment to person A about person B’s bad behavior, “A” embarks on a lengthy explanation of how “B” might have come to be that way. In essence, person A is defending B’s behavior by detailing B’s dysfunctional childhood or the hard times B is going through, making it seem a natural consequence of their history. But does understanding bad behavior mean that we need to accept it?

For example, I was having dinner with old friends when one woman started complaining about her elderly mother whom we all knew from an earlier time in our lives. The complainer was giving some pretty clear examples of the harsh treatment she was still receiving from her mother when another friend piped up with all the reasons Mom might be as she is. I kept my mouth shut for the most part and continued to observe the conversation, wondering how to balance compassion for what someone has gone through with how they treat others—and where we must draw the line.

Clients often tell me tales of woe about their abusive husbands, adding, “Well, if you knew his crazy family, you’d understand why he’s the way he is.” My work is to help clients have compassion for the early mistreatment their spouse endured, while giving them the support to prohibit abusive treatment of them now. While understanding can generate sympathy, empathy, and compassion, it should not excuse unkind, hurtful behavior that occurs on a regular basis. Of course, everyone goes through rough patches and we occasionally exhibit our not-best selves. However, cutting people slack repeatedly because of their crummy past does both you and them a disservice.

Which brings me to the subject of how we must all take responsibility for converting our lousy childhoods into functional adulthoods. None of us is perfect and we must make room for that in relationships. But glossing over mistreatment by explaining it away and insisting that someone can’t help themselves due to this or that only makes the mistreatment more likely to occur in the future. What’s wrong with saying, “I know you’ve suffered terribly, but making me suffer now isn’t going to change your past” or “I understand that this subject is triggering a lot of emotion for you and that you’re trying to change, but your current behavior is not acceptable to me now and never will be”?

Aim for a balance—to be kind to yourself and others, to recognize that each of us must be held accountable for who we are now, and to understand bad behavior without condoning or accepting it.