Robert Neville copes with his depression and loneliness by drinking heavily (in real life, Matheson was known to be a heavy drinker, suggesting that there might be some autobiographical touches in I Am Legend’s descriptions of alcoholism and depression). Alcohol could be said to symbolize the depths of Neville’s loneliness as the last man on Earth.
Alcohol Quotes in I Am Legend
The thought of forty more years of living as he was made him shudder.
And yet he hadn't killed himself. True, he hardly treated his body welfare with reverence. He didn't eat properly, drink properly, sleep properly, or do anything properly. His health wasn't going to last indefinitely; he was already cheating the percentages, he suspected.
But using his body carelessly wasn't suicide. He'd never even approached suicide. Why?
There seemed no answer.