How to stop an affair?

I'm married and so is my lover- I decided to stop messing with him, and to work on my marriage- he agreed as well- we both love our spouses -even though what we are doing is wrong- I was missing something in my marriage that my husband was not willing to given- until recently- now i have this quilt- but i will never tell him- My exlover and I still communicate- and even though he tells me that he won't try to resume this affair- we are drawn right back to it- he a really good person- with a good heart- we just made a mistake that seems not to go away- what can I do to make him understand that no more means no more?