Lord, grant me patience, because if I ask for strength I will surely kill him.
Don't stoop to his level. You have more class than that. Keep your head up.
Don't do it. Create and nurture a new love for YOURSELF! Don't deny your awesomeness! :-)
You're leaving him, it wouldn't be an affair anymore, but don't get involved 'til you're over the situation.
You're nowhere near being able to deal with that emotionally, but I bet it feels good to just say it.