Van Gogh was ill beyond the cures available at the time and had to be under medical care at one point. Yet, he created a tremendous amount of paintings. He died from a gunshot wound before the age of forty.
Dali may have exploited his own eccentricities and used them as a way to gather attention for his art. Separating the truth from the fiction of his life might be an impossible task. If it's all truth, then I don't know if art is worth it.
After researching these artists, I needed to read something more positive. I had to look up Norman Rockwell. Rockwell painted life inspired scenes, and apparently lived an ordinary existence.
Perhaps he painted from his imagination just as much as Dali and Van Gogh, but art should have room for optimism too.