The words you pick in an argument usually outlast the argument.

Arguments end and the sentences stay. Nobody can recall what got settled six months later, but the one line that went too far is still quotable by both of you, and it sits in the room during every disagreement after it. Heat picks words that are accurate about the feeling and unfair about the person.

In the next argument, stay with what happened and what you want, and leave out everything about who they are. Never, always and the cheap shot about their family are the parts you will be apologizing for. If you cannot hold that line, say you need an hour.