What the Hell Is My Uncle Thinking?

I have an uncle who was paralyzed in an auto accident over 30 years ago. He has always had issues with drugs and alcohol, and his health has gotten especially bad in the last several years or so. (He has had both of his legs amputated, because they got infected.) He has been in and out of rehab centers more than once, but he keeps falling in with the same bad crowd and into the same bad habits. He also went to college for a short time, but he squandered that opportunity and eventually quit. He has also been homeless on more than one occasion and has often lived in public housing projects. And just a few days ago, he was admitted to the hospital, because he was having trouble with his heart. For some ungodly reason, though, he left the hospital against the advice of the doctors. My aunt has been trying to persuade him to go back to the hospital, but he refuses, and she says that he looks the same way my grandmother did before she died of congestive heart failure. What is he thinking?
Why does he keep defeating himself? I hate to say this, but I think his days are numbered, and 48 is a very young age at which to die!