I am glad that he is being realistic and pragmatic about this. He is not running a Quixotic Nader-eque campaign, he recognizes that even if he does not win the nomination he can raise the issues of wealth and income inequality and also prompt Hillary to move left
I think this is a major difference between Sanders and other candidates like Nader, Kucinich and Gravel, he has realistic expectations of his candidacy and is using the campaign to draw attention to issues and not just to stroke his own ego. It also helps that he is not particularly whacky or weird, he's pretty grounded and down-to-earth for a socialist. He knows what issues speak to people and how to talk with them and not at them.