I've posted very little here, though I've lurked here awhile.
My wife had a brief affair more than a decade ago, but we're fully reconciled and very far past the crisis. I have some opinions on the topic, though I'm just some random nobody.
I offer this perspective with a caveat–– it applies only to marriages in which there was only one affair, and it requires that the WS, having committed to reconciliation, feels genuine guilt. It does not apply to marriages torn apart by serial infidelity on the part of a WS. (God help anyone married to someone so broken and self-absorbed.)
After an affair, both the WS and the BS are extremely vulnerable to jealousy, though very unique strains of it.
BETRAYED JEALOUSY - A wounded jealousy. This is a jealousy of trauma, one which drives the victim to imagine both past (and possibly real) unconfessed betrayals along with future ones.
NOTE: This is HIGHLY DEBILITATING yet ENTIRELY RATIONAL, as an affair is nothing less than the confirmation of their greatest possible fears. The BS is often powerless to fight the compulsion towards paranoid thinking and they need and deserve the wayward's help to combat it.
BETRAYER JEALOUSY - A selfish jealousy. This is a jealousy of guilt, one which recognizes (to some degree) that depth of one's betrayal. This indicates, in some fashion, the self-centeredness of the WS. He/She is putting themselves in their victim's shoes, and imagining how he/she would "get even" in such horrible circumstances.
NOTE: This is a HIGHLY DESTRUCTIVE "defense" mechanism which is inherently offensive and hurtful to the Betrayed Spouse. Absent clear evidence, the Wayward Spouse has NO RIGHT to question the trustworthiness of the very person who has already proven their trustworthiness to the very person who has already proven their untrustworthiness. Consider the humbling prospect that you married someone of far greater character who simply treats you better than you can imagine treating them. (Lucky you, unlucky them!)
In my opinion, the burden to alleviate BOTH types of jealousy is entirely on the WAYWARD SPOUSE. Period.
Here's what I suggest:
BETRAYER JEALOUSY: Unless your BS has actively given you cause to suspect a "Revenge Affair", this jealousy is an indicator of your own egocentrism, just as the affair was. GET OVER IT AND KEEP IT TO YOURSELF. Do not make accusations or even suggestions about this possibility to your BS. It will only reinforce in his/her mind your self-absorption, which you've already more than demonstrated by betraying him/her. He/she is looking for you to prove that you can change to be a better spouse, not be an even bigger jackass than he/she fears!
BETRAYED JEALOUSY: Your BS has every right to be fearful of possible past undisclosed betrayals. Make sure you have fully accounted for your misdeeds. (I can't overstate the importance of full-disclosure as a foundation for reconciliation!) The BS also has every reason to believe you think him/her utterly worthless and doubt your trustworthiness going forward.
You must be an open book, surrendering yourself to any form of monitoring they require. This will help alleviate their potential for jealousy and suspicion. (I know these points are reiterated everywhere on SI but it can't be said enough.)
But it is every bit as important that your dealings with your BS, in private and especially in public, reinforce to them (and the world) that you value them above all others. If you are both at a party, surrounded by men and women, stay close to your BS. Keep an arm around him/her when you can (if they let you!) Let them know, and anyone watching you, that your spouse is the center of your universe.
It helps SO MUCH for your BS to see you sending signals of this kind to others, especially those people who might look, in their paranoid eyes, like future affair partners waiting to bonk you.
I would encourage any Wayward Spouse who struggles with jealous fears of potential payback from their BS to really examine your own heart. Don't weaponize the guilt you feel; if you do, you cheapen the priceless gift of forgiveness you've been given. The proper response is gratitude, both earnestly felt and visibly demonstrated.
If you fear he/she might be disloyal to you at some time down the road, do everything in your power to show you value him/her more than anyone else ever could. This is what they longed to believe when they forgave you for doing the opposite. This is what you both swore to do when you married. And this is the new foundation your marriage will be built on, amidst the rubble left of the old.
John 8:10-11: "Then Jesus stood up again and said to the woman, “Where are your accusers? Did they not condemn you?”
“No, Lord,” she said.
And Jesus said, “Neither do I. Go and sin no more.”