The life of constant illness

So I have been dealing with gastroparesis for just over a year, and I've only known it was gastroparesis since May. This life is strange and confusing, and I'm exhausted and tired of feeling sick. I tend to feel like I'm not good enough because dealing with this and depression sometimes takes everything out of me.  I feel like I can't get everything I need done, and that my life is going to crumble around me because of it. I'm barely getting by, and being sick just makes it worse. I don't know what to do about it, and some days it's prefer if everything was just over, but to tell anyone who hasn't felt this way, or dealt with these things, just gets me hlepy advice. "Just smile it will get better", "get out and do something", "don't dwell on it", "do what the doctors say so you feel better". All said in kindness, meant to be helpful, but ends up making me feel more worthless, more pointless, more like I'd be better off not existing. I cannot keep feeling this way. It is a miserable existence. I just want to be done.