Teal'c: Nothing I have done since turning against the Goa'uld will make up for the atrocities I once committed in their name. Somewhere deep inside you, you knew it was wrong. A voice you did not recognise screamed for you to stop. You saw no way out. It was the way things were; they could not be changed. You tried to convince yourself the people you were hurting deserved it. You became numb to their pain and suffering. You learned to shut out the voice speaking against it.
Tomin: There's always a choice.
Teal'c: Indeed there is.
Tomin: I chose to ignore it.
Tomin: I sit here... and I cannot imaging the day when I will forgive myself.
: Because it will never come.
One day others may try to convince you they have forgiven you. That is more about them than you. For them, imparting forgiveness is a blessing.
Tomin: How do you go on?
Teal'c: It is simple. You will never forgive yourself. Accept it. You hurt others, many others. That cannot be undone. You will never find personal retribution. But your life does not have to end; That which is right, just, and true can still prevail. If you do not fight for what you believe in, all may be lost for everyone else. But do not fight for yourself. Fight for others, others that may be saved through your effort. That is the least you can do.