Don't ever be afraid to ask for help, encouraging words, positivity or whatever you need. Nobody can help if they don't know you're hurting.
I suffer from mental health issues as well and, well, right now I'm really struggling. So I understand.
I also understand how you feel about your grandmother. But, try to think positively. A few years ago my grandfather was really in bad shape and ended up in the hospital.
Long story short... The whole family as well as his priest were called in to say goodbye, and read him his last rites. We said our goodbyes and headed home, confident he would be gone by morning.
Well, morning came and I called my Dad... No word yet. So I headed to the hospital to find him sitting up eating cereal. He asked what the hell everyone was there for, hahahaha.
Anyway, he made it through. It was a tough road full of months of hospitals, rehabs, etc...
That was EIGHT YEARS ago this month. I'm happy to say Pepere is doing great. He'll be turning 99 in July and still lives at home.
My point is, don't give up hope.