In The Death of a Salesman, what compels Willy Loman to commit suicide, for the sake of his family?

In Arthur Miller's Death of a Salesman, Willy Loman commits suicide in the end because he has lost all hope. He has spent a lifetime trying to be a successful salesman who is well-liked. However, when this doesn't happen, and his sons do not succeed either, Willy does not know what else to do. 

In the end, he commits suicide because he is no good to his family. He thinks they would be better off without him. He is also in so much debt, he knows he will never be able to pay it back. He feels that he is no good to his family or society. 

Unfortunately, Will never valued his role as a father and husband. He always got his identity from his work and from his notions of success.