Our serious wrongdoings leave scars on us and have the potential to change our character permanently. Other people’s wrongdoings (or sins) also leave us scarred and hurting. We can experience resentment, bitterness, anger, despair, etc. Interestingly, these feelings don’t hurt the person who hurt us, only ourselves.
The Sacrament of Reconciliation (or Confession) enables us to seek forgiveness and mercy from God for our wrongdoing and to choose to reject our resentment, bitterness and anger towards others. It is therefore a valuable gift from God for our healing; just like doctors and specialists.