"Lydia, you are my best friend and I would never do anything to intentionally cause harm to you or your marriage. Through some series of events however, I happen to discover that I have feelings of more-than-just-friendly love for your husband. Since this feeling has been acknowledged as mutual, I would like nothing better than to find a way to make this work for all of us. I do not wish to bring misery into your life - I want to work together to bring more happiness into John's life, and hope that by doing so that we might even realize a deepening of our friendship. It was never my intention to "steal" your husband from you, and I understand that you probably feel pain and betrayal to a certain extent. I am sure I would feel similar things if I were in your position. Can we please figure out a way to move forward so that we might eventually arrive at a dynamic we all feel comfortable with? I know you said you need some time - a "break" you call it - for us to all clear our heads and figure out what we need from each other. I have so much respect for you as a person and as a friend, and John is such a wonderful man that he is worth the extra effort and deserves two women who love him so much, that I would like to take you up on your offer to get some space in order to try to work things out. You are such a generous wife, partner, and friend to have opened yourself to sharing your husband with me; not many women would do that and I will try to do whatever I can to not come between you and John because I value your friendship as much as i value the new level of relationship I have discovered with him. Please tell me what you need from me in order to give this a chance to work.
Anything less than that is unacceptable, as far as I'm concerned.