"The rest of your life is an eight o'clock class," a colleague of mine likes to say to the new graduates he counsels. It's a delightful metaphor, but I think that makes it sound too easy. It suggests that, in your professional future, just signing up and showing up will be enough.
As you've no doubt learned during the last four years, it's possible to take a course, pass it, even get a good grade in it, without being fully engaged. This behavior will not work for you in today's workplace. Anyone who takes a passive stance puts their job status at risk.
Back in the days when recruitment out of college led to a progressive career track with the same company (IBM, GE, AT&T, etc.) it was valid, but in the competitive, global marketplace you are entering today, it is not.