You have an affair because you are not getting what you want from your loved one. You want more: more love, more sex, more attention, more fun. You want someone to look at you with lust - after years of laundry - transforming you into something radiant. You want it, you need it, you owe it yourself to get it. To live any other way is to be muffled and gray and marching meaninglessly toward death. You want what she gave you at the start (but what you had hoped would expand and intensify instead of shrinking until you find yourself so sad, so resentful, you can barely stand to be you). You have an affair to get for yourself what you wish would come from the person you love the most. And then you have broken her heart and she can never give you any of it ever again.