Try relieving others' of guilty feelings by having a short memory for perceived past transgressions. In not holding the past over others, you are offering them the grace and generosity to be their best self presently.
To prevent your own future guilt, try refraining from condemning others or judging harshly. Fantasizing about how what comes around goes around paradoxically results in your own guilty feelings as well as fear of retribution because this process is circular.
In summary, have a short memory for perceived past transgressions, try giving others the grace to be their best self by not holding the past over them, and refrain from judging others. You will feel lighter and more joyful.