Not to negate the enormous, devastating grief of losing a child to death......however, I've read quite a few times on this site parents stating that they considered letting go of a person who is alive to be more difficult.
What you've had to let go of newstart is beyond comprehension.. ...your mentally ill in laws, your son, your daughter.
I'm so sorry.
Some of us know grief more intimately..... it's been a part of our lives for so long. I think that's why I relate to your story so deeply, I too have had to let go of most of my bio-family because of mental illness.....it can tear your heart up in a million pieces from the sheer powerlessness and profound sorrow.
That's been my experience around grief as well, it comes in waves, it's intermittent, sometimes more intense than others. My best advice, which was told to me too, is, lean into it. Go with it. Express it. We here have an ocean of grief within us because of our troubled kids.....let the grief out, don't harbor it, it's much healthier to express it.
I think Tanya said it well. We can find meaning in our suffering. We can share our stories. I've unwittingly become someone well versed in how it feels to be around mental illness.....I can offer my story up to those still struggling.....as you are doing....as we are all doing.....healing ourselves as we support others to heal themselves.
I think you do know what to do ......and you're doing it. This is it. Setting boundaries with your daughter and practicing detachment. That's what we're all doing. It's a whole new ball game and it takes a lot of practice to learn the rules of this one.....when I look back at when I first arrived here, I felt much as you do.....I actually could not imagine feeling any differently.......but.....I do. You will too.
Hang in there. There's light at the end of this tunnel. You're not alone, we're here with you.