Well, if you aren't willing to sacrifice, they you will ensure that the system continues as-is in perpetuity. Somewhat cowardly, IMHO ... but do what you think is right.
And if Kerry happened to win, dare I say you would notice very little that is different right now. Maybe a few things here and there, but for the most part - your life would continue as it has for the last 4 years or so.
Let's not go nuts. The two major parties have few practical differences. Currently, we just vote in the people who take the bribes. Elected officials don't make laws. Lobbyists do.