I will never take a single vote for granted considering how many elections in very recent history were literally decided by a single vote.

It's even important to vote in states and districts that are deep red/blue where the minority party is statistically unlikely to win, because if you don't show up the numbers will never reflect the true demographic of people who want a change. Not to mention the arguably more important down ballot races for local elections. Change on a macro scale might be difficult, but change on a local level is very possible.

The way I look at it is yeah your one vote doesn't count for much, but consider this; if you can convince 5 friends to join you in voting for the same candidate, that's 6 more votes that the opposition will also need to scrounge up just to win by the same margin as if you did not vote at all. That's not insignificant. Using your right to vote can swing the social dialogue more towards compromise in future elections if enough people turn out.