I agree with Leaf practice radical acceptance.

What I learnt on the forum is our situations are unique and it helps to understand others situations we learn from and provides us context and enlightment.
My DD was diagnosed at 26, 2015, she hit rock bottom, was very ill. She was desperate and I said there is help out there. It was her only option and she took it, grabbed on with determination to live. DBT, refreshers and then therapy that included trauma and continued use of DBT skills. Four years. DD beat her eating disorder, alcohol addiction, self harm...it is a journey for sure and takes patience and resiliance

.
I asked DD back in 2016 why she did not seek help ealier such as 18. Answer - the thought of talking to a therapist -I was not ready. Living the life of young adults, as they do.
Working on the communication tools is very important, some which feel unintutive and take practice... Many members sign up to FamilyConnections
https://www.borderlinepersonalitydisorder.org/family-connections/I hope this helps and gives you hope.
Is your son living independently, he is holding a job down.
WDx