How to protect yourself from the worry and pain of watching your adult child suffer

Hi everyone

My son is now 20, intellectually brilliant/ anxious. He's had a rough time with mental health and various aches and pains. ( Autistic/ adhd .

refuses to let me help/ talk about any of the above)Last year he finally got proactive and has had 2 MRI s.. rheumatologist thought it may be fibromyalgia but the 2nd MRI is suggesting ankylosing spondylitis so now he needs a CT scan. He doesn't want to talk about it, but in his own time I know he'll make the appointment.

My question is: how do you separate yourself from the pain of seeing your child, (even though he's an adult ) suffer ..this pain/ fear/ helplessness that I am feeling is non-stop agony for me. I can't stop crying and I fear it will make me mentally ill as well! I know intellectually that it is totally useless.. but the pain doesn't hear that. Any strategies for self preservation?

Thank you, and I do feel for all of you out there watching loved ones struggling.