As the unfaithful husband, I found that my wife's diminished response to the special things I did, created disillusionment in me. I did not "try" to gain favor with her, nor illicit her thanks and praise. I simply followed through with gifts and tasks that made me think lovingly of her. She tended to be kind of underwhelmed. My affair partner was quite the opposite. Gifts and tasks done for her was met with great elation! I felt very appreciated and celebrated. So, it became increasingly easier to serve my affair partner (even though it was wrong), thus I didn't even bother with my wife (which was wrong.)