Parents, I need your help... How would you want your child broken up with if it became necessary to have a break up?

I’ve never broken up with anyone I’ve been in a ‘romantic’ relationship with before except for one person… when I was angry, because that guy treated me disrespectfully. So it was easy. But if your child treats his or her significant other with respect and the only issue is that things aren’t working out, but otherwise he or she is a fantastic person, what is the best way to end it? Why is this so hard?