I think you need to allow yourself to be sad by your son's departure. You also need to be sad that you weren't the man you are now when you were w/S12.
However, you also need to know that S12 can see the growth and change in you and he is very proud of what you've accomplished. You have told us what S12 has said to you and it is very obivous that he knows you love him dearly and have always done the best you could w/him.
Thus, I guess I can only say that you need to remember that you did the best you could under the circumstances you were faced w/based on the information you had and the skill sets you possessed at the time.
You can learn from the past and become better for the future, but you can't live regretting what could have been. All you can do is focus on what is and what will be.
