This can increase dopamine in the brain and help to reinvigorate romantic love
If you're the one who has had the affair, understand that your partner will be hurt, angry, in love with you, in hate with you, miss you, never want to see you again, won't want to be without you – and sometimes this will turn so quickly you won't see it coming. Stand still and let his or her emotion wash over you. There will come a point where this will stop but in the meantime the high emotion has to come out, otherwise it will fester and rot your relationship from the inside you. You don't want that. And be loving. Always.
Do something novel together.
When the time is right, do something novel and exciting together. Go away for a weekend somewhere you haven't been before, do something together you haven't tried before, if your relationship has been without sex for a while bring it back.
Relationships that have been broken by the intrusion of another can heal, provided that both people are able to feel safe from blame and shame enough to own their part in the breakage.