Throwing away your vote is a sure fire way to make things worse. Vote for the candidate that has the highest odds of winning who will make things better, or at least not worse. Just because you don't like the candidate on the "left" doesn't mean they're not the one that will objectively do the least harm in office. Letting Trump or anyone else on the right in office is objectively bad on so many measures.

Voting third party is morally reprehensible. Even if it makes you feel better, it's worst for all of us. Don't be selfish.