Best single piece of advice for a college student entering the workforce?

The title is pretty self-explanatory. I am currently a college student who will be 21 in December and although I am in the process of interviewing for full-time or internship spots, I have still not received a job offer. I am trying to do everything correctly and follow in the footsteps of successful people I've met, but I would love to hear from people who are currently in the workforce about what advice they give to students who will soon be finishing their education.