In the movie Valentine's Day, an old woman confesses to her husband her short-lived infidelity done years ago, thus, risking their supposedly happily-ever-after-marriage. When everything is going great, and what the other doesn't know won't hurt him/ her, wouldn't it be safer to keep everthing to oneself and let go of his/ her past, especially, in this case, that she is sincerely sorry and regretful of that past? I think the reason why quite a number of people own up (and they sincerely feel the need to) to their 3rd party affairs themselves is that because the only way they could forgive themselves and finally move on from that ugly past is to be assured that their partners could find it in their hearts to forgive them, too, while continuing to stick by them and never letting go and giving up on their relationship inspite and despite of the hurtful history. Truly, love is unconditional, and it's essence includes forgiveness of even the gravest of sins.