Accept the truth from your partner
Plan both kinds of outcome of your talk – negative and positive alike. You cannot read your partner’s mind even if you have been with that person for a few years. It is great if you hear how sorry your partner is and that they will never ever do the same stuff again. On the other hand, your partner‘s infidelity can be love they feel for someone else and then they will want to leave you.

Your partner’s infidelity is not your fault
Your partner has no right to blame you if you have always been loyal and infidelity comes from their part. If the person is weak and cannot accept his fault, do not let them make you feel guilty. You cannot be the reason of their unfaithful behavior. This is simply their true nature and that happens to many people where only one partner is unfaithful. You deserve to feel respected rather than blamed by someone who has been dishonest.