Darling, look at the stories of the rescue dogs we have between us on MN. Some of them have been through hell and back but they DO recover, our stories prove that and I see it myself in rescue.
I've got 3 big dogs -
Labrador - Beaten by alcoholic male owner for first 2 years of his life. Had real issues with men. Rescued and adopted by a woman, rescue being assured that no man would live with him. Stayed with her for 2 years, she moved violent BF in, Labrador hurt again, taken to vets for PTS, vet sent him instead to rescue, rescue couldn't get near him, he was snarling and aggressively barking, growling and trying to bite through the kennel.
I came along and we somehow clicked - I only went to the rescue for a fete, not to adopt a dog! Moved him in with my young children. other 2 dogs and I... he's wonderful, loves us all, happy and content and has been here for nearly 8 years now.
GSD 1 - came to me as a 6/7 week old puppy as purchasers didn't want him. Mine his third home, he's 4 now and daft as a brush, loves everyone.
GSD 2 - lived with a lone mum since being a pup, put into rescue due to change of family circs, stayed there 18 months, scared of everyone, literally no-one could get near him, he'd just run away. I worked and worked on him, spending whole weeks in rescue, made him my friend. He's epileptic and had had some fits whilst in kennels.
He's been living with me for a year now. He's loyal, content, snoring as I type, has great recall, never runs away or goes far from my side, is happy now to allow most visitors to fuss him.
So yes.... they do get over upset and grief, I promise.