Course Withdraw Question?

I'm a senior at college and currently in my last semester. I'm currently taking 6 courses and the work load is quite heavy. Today I had a sociology midterm (elective course) which I already know I didn't do good on. Would it seem bad to graduate schools if I withdrew from the course and got a W on my transcript? I have never withdrawn from a course, so my transcript is pretty clean. I can't risk getting a D (or even worse F) but also intend on applying to grad school next year and wouldn't want a W to affect my acceptance. What should I do? I've been stressing over this matter all day!!!