Those "why" or "I feel rejected" or "how can you do this ~ that is why I do what I do" conversations always did me in too, Stands.
It helped me to keep my focus on the long-term outcome. Once I had acknowledged that the root of the problem was not poor parenting but drug use, I was able to go back to that truth again and again. From that place where I could understand how it all started, I could stand up and remember why I needed to say no, or why I needed to interact with my son differently. It never feels like the right thing, and our son never once said "Oh! NOW I get it."
It felt very lonely to interact with him in that way.
But once I understood where the behaviors that were destroying my son were coming from, and once I realized that it hadn't been some failure on my part, I understood too that taking the positions I took relative to our son were the only possible ways I could help him see who he had become.
Your son is so much more than the person whose choices led him to be where he is, Stands.
That is what you need to draw strength from.
That is what helped me to be strong ~ remembering who my son was before he changed, and believing in the man he will become if he can beat the addiction.
The other thing that helped me ~ maybe the thing that helped the most ~ was to refuse to entertain the feelings attending any interaction with my son.
I have posted about that before Stands ~ for me, that is the point where I began to be able to pick myself up emotionally.
It helped me to remind myself that there were no easy answers and there were no short cuts, and that what was happening in our family was truly tragic.
Somehow, thinking like that enabled me to give the pain its limits.
And that enabled me to function despite the overwhelming pain.
Wishing you well with this part, Stands.
You know I believe you can do all that you need to, to see this thing through.
Barbara