Stephen Crane (1871-1900) was an influential American novelist, poet, and journalist known for his realistic portrayal of war and themes of fear, spiritual crisis, and social isolation. His poem 'The Heart' explores the notion of individual loneliness and the struggles faced in life, using vivid imagery and striking metaphors to convey a somber tone. The poem suggests that individuals must confront their own pain and bitterness, implying that true responsibility for happiness lies within oneself.