There seems to be a widespread belief, especially among those who've hurt others, that with forgiveness comes a restoration of trust. In other words, if the offended individual doesn't trust the offender and resume the same relationship with them, then the offended person has not truly forgiven. Nothing could be further from the truth.
Forgiveness is letting go of bitterness. It is feeling brotherly (or sisterly) love toward someone who has wronged you and bearing them no ill will. That's it. That's all. It does not entail putting them in a position to hurt you or let you down again. It does not entail sparing them from the consequences of their actions. Forgiveness should be freely given. Trust must be earned.
The Lord commanded us to forgive. He never commanded us to trust.
The Difference Between "Letting Go" and Letting Someone Hurt You
If I hire a babysitter who neglects to feed my children and to change the baby's diaper, I can let go of my anger. I don't have to try to ruin this person. I can give them my feedback. I don't have to gossip about them (although I may warn other parents who ask my opinion). That's forgiveness. However, I'm not going to invite this person to watch my kids again, because he or she has lost my trust.
Abusive and/or unfaithful spouses, family, or friends often want their loved ones to forgive them, falsely believing that forgiveness will make the relationship "like it used to be." What they fail to see is that, if their relationship is to heal, it will only occur by regaining trust, which often takes much longer than it does to forgive (i.e. letting go of malice and the desire to punish).
Sometimes the person who was abused and/or cheated on justifiably ends the relationship while saying, "I forgive you." This is totally consistent because forgiveness is replacing hate with love and wishing someone well not restoring them to a position where they can hurt or betray you again.
Elder Jeffrey R. Holland masterfully taught:
“'Forgive, and ye shall be forgiven,' Christ taught in New Testament times. And in our day: 'I, the Lord, will forgive whom I will forgive, but of you it is required to forgive all men.' It is, however, important for some of you living in real anguish to note what He did not say. He did not say, 'You are not allowed to feel true pain or real sorrow from the shattering experiences you have had at the hand of another.' Nor did He say, 'In order to forgive fully, you have to reenter a toxic relationship or return to an abusive, destructive circumstance.' But notwithstanding even the most terrible offenses that might come to us, we can rise above our pain only when we put our feet onto the path of true healing. That path is the forgiving one walked by Jesus of Nazareth, who calls out to each of us, 'Come, follow me'” (“The Ministry of Reconciliation,” October 2018 General Conference).
In your life, it is good to be forgiving. It's good for your emotional and mental health to abandon bitterness. Where an offender is truly repentant and displays it with their behavior (and where you or your children desire a relationship with that person) it is good to mend fences and restore connection. However, it's also healthy to protect yourself from repeated neglect, disloyalty, or abuse of any kind. Boundaries can be set and kept. Forgiveness is not the same thing as trust. And trust can only be restored when the person who wronged you is repentant, acknowledges the pain they caused, and is willing to take the time and do the work to earn that trust.