I shall remove the heart of stone...and give you a heart of flesh (Ezekiel 36:26).
To tackle our failings may be quite painful in a group and must never be forced. It is painful enough to do alone! But that is still no reason for not learning how supportive a prayer group can be in the more difficult parts of life.
You might become more aware of the difference posture can make. Most prayer groups sit to pray but if we are considering forgiveness it might be helpful to emphasise the activity by kneeling.
A painting of the crucifixion or a crucifix may give a focus to the prayer as we kneel.
While kneeling at the foot of the Cross we can talk silently to Christ on the Cross about our need for forgiveness, or the struggle we are having to forgive, or to be reconciled, and we can allow our Lord space in which he can talk back to us.
Still kneeling there - ‘being present to the Cross’ - we allow the hardness, the bitterness, the anger, the resentment which we find welling up inside ourselves and knotting us up, to flow out of us on to that figure on the Cross, and to feel love flowing back from him cleansing, love, and forgiveness.
Sometimes people may have a need to be reconciled with a particular person or with a group of people, in which case they can imagine themselves standing or kneeling at the foot of that Cross with those people and allowing the aggression to flow on to Christ on the Cross, and again to feel his love flowing into them and being drawn to them.
A very simple alternative exercise in forgiveness, also suitable for use in retreats, and especially for married people, is to go out of doors and find for yourself a stone which will represent to you something which you want to give up, like anger, bitterness, or resentment. You then kneel at the foot of the cross, or before the painting, clutching the stone with its symbolism. You are likely to hold it in your fists as though it were your last treasure, but when eventually feel you can, you go to the Cross and place the stone there.