How does the novella end in optimistic tone?

Mr. Bellow describes Tommy Wilhelm (born Adler), a 42-odd- year-old salesman who, despite a wife and two children, has not learned to think of himself as a grown and independent being. Separated from his wife, jobless because of his own impulsiveness, bedevilled by money worries, resentful of his father for withholding both cash and emotional protection, he has tied himself to a quack psychologist whom he profoundly distrusts — all the more because he cannot shake himself loose of the man’s preposterous but haunting counsels. 

Tommy finds himself prowling through a New York day searching for a place of support or rest. By the end of it, he has tossed away the last of his money on the market and is desperately frightened. Yet he gains an unexpected release when he is swept by the passing crowd into the funeral of a man he has never known -and, looking down at the dead man’s face, at last finds himself able to feel, to accept his own suffering. Thus, at last, he is able to confront that larger suffering which (as we can see only at the end of the story) has been the dead weight of existence pressing on him without any release or passion in him of understanding. 

It is the intense world of the ordinary, the mean daily detail, the outrage of being alive, the existential sense of one’s self as human creature, which is bravely at the centre of Mr. Bellow’s fiction. Each detail is cruel, plain, irremediable, yet one feels that it is about to burst forth into the radiance of consciousness.