Here's mine for a starter - sent in December 2005 and still in it - with the odd lapse - I am sure it can be improved upon - but it still makes me cry when I read it!
It is truly sad what has happened to our marriage and us, and the path that I must take now is not one of choice but one of self-preservation.
I know I have made mistakes in the past and I am truly sorry for helping to create an environment that has made it possible for your affair. I do know those things I was lacking in - I just didn’t understand how important it was to us.
The past few months have been the most difficult time of my life. The pain and emptiness that I endure on a daily basis is almost too much to bear. My only consolation is the memories of the love we once shared, of the all good times we have spent together, your extraordinary qualities that led me to commit to spend my life with you and thoughts of us being together, someday happy again. Unfortunately, I now find those thoughts and feelings are slowly eroding away. Before I lose any more of the thoughts and feelings of what was once us, I must take some drastic steps.
As you know I am still willing to do whatever it takes to correct the mistakes that we have made in the past and make our marriage together stronger and closer than we ever thought possible. With all of my heart, I would like to build a new marriage with you. One, in which we both feel loved, safe, and cherished. I simply cannot continue my efforts to rebuild our marriage while you are still involved with another person. It has become too painful. We can only rebuild our marriage, together, when you completely end your relationship with her.
Until that point, I feel I must break off all contact with you. To this end, I feel it is best that you find another place to stay, while I continue to stay at our home. I will avoid seeing you or talking to you or communicating with you in any way.
I ask that you respect my decision to separate from you in this way. You must know the deep pain and humiliation I have endured because of your relationship with another woman. I simply cannot be in contact with you any longer and this separation is a necessity to preserve my love for you, to avoid poisoning all that we have shared together, and to give our marriage the best chance for recovery.
I will be willing to discuss our future together as soon as you are
• willing to permanently separate/have absolutely no contact with her, and
• willing to construct a plan to ensure a complete separation from her.
I have loved you in many different ways; as a girlfriend, as a wife, as a confidant and as a friend. I still love you today; I just cannot be with you or help you as long as you are still involved with someone else.