I agree. Like your mom, I worry about what will happen when my partner is gone. He is everything to me. But then I have to pause and tell myself that he still is here right now and I must not waste my time in a future without him when I can reach out and hold him any time I wish. Do we need to have a plan for the day when we are alone? Sure. But do we need to dwell on it? Of course not. Every day brings new grace and strength that we didn't think possible. I realize that in the future I will have to surround myself with friends and family, although I am not close to them now. So, getting in touch with people and occasionally talking to them is good. Keep the lines open. You'd be surprised at how people want to be there for other people, they're just caught up in their daily activities, but can and will reach out to those who wish to be a part of their life.
The past is full of hopes and disappointments. It doesn't have to be a roadmap for the future, though. Recovery is always possible, however small our gains seem to be.
You're not alone. We're all struggling through our illnesses together. Don't give up.