Struggling to Give My Pet Away

I have to give my pet away. I have owned a bird now for a year and a half and we’ve bonded a lot, but he is now very sick and the vets still don’t know why even after a couple thousand dollars in vet bills, and it’s stressing me the fuck out. I also really poorly planned it when I bought him, I didn’t consider how difficult it would be to be an emerging adult looking for colleges and homes to go to while trying to keep my bird. My mental health this year too has been down the drain, to the point where I’ve considered checking myself into a hospital multiple times (if American hospitals weren’t so abusive). I haven’t been giving him any attention at all these past few weeks and I don’t think I will be able to at all anymore. I’ve cried a lot over this bird, he’s one of my best friends, but I am now trying to give him to a special needs foster care to fix him up without having to worry about cost, and finding him a forever home where he can be given attention. I really really struggled to come to this decision, and I am dreading the day I see him for the last time. Any tips on how to cope with the loss of a pet, and maybe how to soothe my anxiety that he struggles to recover his health and find a loving home? I only want what’s best for him, and I’m fully aware that isn’t me.