If you voted based on mathematics, you would see that you are mistakenly conflating your individual vote with the behavior of the general populace. For example, with the presidential vote, except in a couple small districts in swing states, your vote is completely irrelevant. Your single vote is both not enough to swing the state you are in, and even if it were, it's within the error margins for that state. If it ever got close enough to where one vote decides it (and it never has), it would be a court deciding the vote anyway.

So since your individual vote doesn't matter, you might as well vote your conscience and not pragmatically.