After all, everyone will lie in the same bed he does. Moreover, his death is not final. As his lover, Annie, looks on him and cries because she thinks he is dead, he declares that his heart and his thoughts are more alive than ever, for they are filled with the sight of Annie's love. Though dead, he lives on because of her love. The poem reverses ordinary ways of thinking about death and life.
Life is an illness and death is a cure rather then visa versa.
Death is also not just a matter of body. The man's mind and heart are alive even though his body is quite dead.