Someone posted on the forum that they are working the 12-Steps and making progress, but every time they remember the terrible sins they did and the harm they caused others, they become depressed and even suicidal, thinking of the irreversible damage that was done.
"Smile4Life" replied:
All I can do is just share with you a quick story I heard about a certain gadol whose father was very ill and he would sit at his bedside day and night so that he would not be alone. One night, this rav's children (the sick guy's grandchildren) came to him and told him that they would sit by zeidy for the night so that he should be able to get some rest because he was tending to his father all the time. After he refused a number of times, they finally persuaded him to get some rest. That night, the rav's father was niftar. When the rav saw that his father passed away he was convinced that he murdered his own father. He said that his father saw him at the bedside all the time and that night when he looked and saw that his son was not there, he figured that his son had given up on him and he therefore died. He was taken to many rabanim who all tried to convince him that it was not his fault, but it didn't do anything and he was so miserable because he really thought he killed his father. Finally he was taken to the Chofetz Chaim (I think) who after failing to convince him that it was not his fault, told him like this: "Fine. Let's say you did kill your father. But guess what? There is something called Teshuva and you can make it as though you never killed him. Don't give up and it will be alright." Just that bit of chizzuk made the rav so happy and he was able to do teshuva and go back to normal.
I think the same message applies here. The gate of Teshuva is always open and especially when there are tears, for the gate of tears are never closed and there is always a way back. Just hang in there, put on a smile, and it will be alright.
I heard a similar story with the "Yenuka" of Stolin (Rav Yisrael Perlow Zatza"l), who was approached by a man who also felt he had killed his father. This man had suggested that his father undergo a certain surgical procedure, which had resulted in the father's death. "If only I would have not suggested it", the man bemoaned, "my father could have still been alive". The Yenuka answered him as follows: The words "would have" and "could have" are Keffirah.
A Jew has to look at the past as orchestrated by Hashem. Yes, even our sins - in a sense. When doing Teshuvah, the focus should not be "If only I hadn't done that", but rather "How can I be different - and fix the past - with my actions NOW".
We only have the NOW. We need to look at each moment as if we were just born, and as if our past is being given to us NOW as "a package" to fix.