Just read an excellent article giving Bernie credit for how much good he's done and can still do, even if he doesn't get the nomination.
He has definitely pulled Clinton to the left on the trade agreement, wealth disparity, public option for the ACA, the Keystone Pipeline...
The article by Jamelle Bouie makes the point that Sanders should stay in the race and continue to make Clinton fight for the nomination. Beyond that, if Bernie loses, he has made such a big impact that he could carve out a 'Sanders wing' of the Democratic party, holding Clinton accountable, supporting other down ticket candidacies to create a Democratic-controlled Senate, using his newly elevated profile to improve government for the better - even if he can't do it from the oval office.
That may not be the cataclysmic revolution that his followers hoped for, but it is the right direction. And it is a very good reason to not give up fighting, if he loses this particular battle.
http://www.thedailybeast.com/cheats/2016/02/28/trump-won-t-denounce-kkk-support.html