If the wandering partner feels the need to confess, he or she should confide in a priest, doctor or counsellor. Off-loading guilt on a spouse will not help anyone and may even precipitate the end of the marriage after all. The early days of an affair are usually all about illicit excitement and sex. And it's quite common for the participants to believe that they can control what's happening and just have a harmless bit of fun. Minds get involved as well as genitals.
Love develops out of sex.
And people start to want more time together, enjoy more and companionship and frequently a future. Relationships don't stand still. People having affairs learn this the hard way every day. And life gets more and more complicated and painful as a result. The short answer is that it's not at all likely.