Don't pretend. Don't make up pretty reasons. No matter how "ugly" the reasons are, they're better straight out to our children, or at least as straight as we can put them.
It's not always easy, however, to get the facts straight.
We ourselves may feel confused about them. Uncertain about what really went wrong. So unclear in our own thinking that it's impossible to clarify the matter to anyone else.
Quite apparently, then, the first step is to put the facts as straight as we can to ourselves.
If you feel confused, try, if you can, to talk the whole thing over with someone. A professional person is best. In any case, talk it over with yourself. Out loud is better than in silent thinking. Even though you may sound silly to yourself at first, as you struggle to put your feelings and thoughts into words they sometimes come clearer. It will then be simpler and easier to share the facts with your child.
" Gina, I'm sure you must have wondered why your father and I separated. I know now I should have told you more about it. But I didn't know this until recently. I thought in an old-fashioned way that I was 'saving you' by keeping quiet. I guess that was silly . . ."
"Yes, Mother, it was," Gina pitched in forthrightly. "Because I've wondered and worried a lot."
When you start you won't need to be long-winded. A simple statement will put the matter out in the open as a first step in the right direction. The important thing is to help your boy or girl feel free to talk about his own feelings and to ask you questions that will lighten his wonderings and doubts as time moves on.
Quite honestly, "Your father loved somebody else better than he loved me," if there was another-woman reason. Or "He went around looking for someone else to love," if it was another-woman-plural deal. Or "We spent so much time quarreling that staying together just wasn't worth it. We figured we'd be more content apart." Or "Being in bed together and loving each other the way married people should in order to feel close and in harmony didn't work out well for us."
Whatever the problem was, or however you see it, be as open and honest about it as you can be.