Whatever happens at the convention, you are already the most important new movement in four decades. Don't give up. Just consider it a slow Bern.
Hillary Clinton is deceitful, manipulative and corrupt. On the other hand, it will be a lot easier to get good things done if she is in the White House rather than, say, Donald Trump or Ted Cruz. She not only will name several Supreme Court justices, she won't build a Mexican wall, be mean to women, blacks and gays, or slash things like healthcare, Social Security and food stamps. So if Bernie doesn't get the nomination, support Clinton as the preferable crooked alternative.
Politics is not religion. This is not about your personal virtue or salvation; it's about the best way to save the country. And in politics, the lesser of two evils is often the best choice you have.
Besides, Clinton doesn't believe in much so the strength of the Bernie movement will have much more effect on her than on Trump or Cruz.
This is not just about an election, it is about a huge cultural change. Check out views by party, ethnicity, and issues and you will repeatedly find a great divide is age. We wouldn't be having the sort of problems we do if everyone was under 45. So hang in there. Time will be on your side. It's just that we can have a lot of trouble before it gets there.
We haven't had a decent counter-cultural movement in this country since punk rock was flourishing. Don't forget music and symbols as part of your efforts.
Organize by issues, not by ideology. When liberals became a semi-private culture that dissed people like older and poorer whites, their power evaporated and they gave the Donald Trumps a constituency. Get it back by organizing around issues. Go after the bad guys at the top, but convert rather than condemn their supporters.
Form active and visible cross-cultural alliances. The older crowd is often stuck in the comfort of their self-identity and the groups that support it. But change is greatly boosted the more friends we find and work with that don't look like us. For example, a young, white, black and latino action alliance backed by labor unions could really shake things up.
Above all, don't give up just because of what happens in the primaries. Take all those email addresses and phone numbers you've collected and build a new movement for a new America.