What opportunity does willy think he missed when he was a younger man?

In Arthur Miller's play "Death of a Salesman," Willy Loman believes he missed the opportunity to become a successful businessman and a wealthy man like his brother Ben, who struck it rich in the diamond mines. He feels he failed to seize his potential and make the right connections in the business world. This perceived failure haunts him throughout his life, contributing to his sense of inadequacy and disillusionment with the American Dream. Willy's regret intensifies his longing for success and validation, shaping his interactions with his family.