Here, let me give you some perspective:
Do you work for the man? Do you work hard? Do you rarely ever take a day off/call in sick? Are you a responsible human being? Do you just feel that you need a break?
If you answered "yes" to any of the above, take the day off. Seriously, you're going to work your entire godamn life, might as well take a break. Your company OWES it to you.
I work for Corporate Express, err, well, Staples now. When Staples took over, they took all of our sick time and rolled it into vacation time (that we had to use by the end of this year) and gave us two sick days to last the last 7 months of the year. Ususally not an issue, except this year I got the flu, and bronchitis right on top of it. Now I'm completely out of sick days, and if I get the flu again, or if I get H1N1, I get fired. I had 70+ hours of sick time before they screwed us out of our time. Been there 3 effing years.
So more than anything, do it for ME.