Considering that the revelation of the betrayal is indeed terrible, there’s absolutely no available space for defensiveness. You are best off utilizing two expressions: 1) «You’re right» (when they’re right) and 2) «we deserve that» (if they are incorrect). Answering the «why» questions is tricky at the best. Any description you give is likely to be regarded as a reason. The best solution for the why concerns is always to inform your mate you may try everything feasible to look for the clear answer, but acknowledge you do not would you like to seem protective while attempting to answer a concern that you don’t always understand the response to. Anything you do, do not be defensive.
At this stage, you may be saying, «I do not wish to just take all of the fault; my partner (or spouse) made her (or their) very own efforts from what has occurred. We’d dilemmas in this relationship well before an affair was had by me.» And while which may be real, your order that is first of has to function as stabilization of this wedding.