The days of avoiding the real world are finally over!
Having recently completed my postgraduate degree, my ultimate advice for those who are currently taking or planning to take one is to ask questions.
The line that distinguishes office from school lies along the opportunity to sound stupid. The essence of school is to teach you what your experienced boss doesn't teach you, what you want to and don't know. And your classes are the only chance you maybe entitled to sound like a dummy (at your age). It will be tough, it will be exhausting, and it will leave you broke. But unlike stock market, it's a great investment you have FULL control of.
Postgrad life is a far cry from college life. So don't come to class with a college mindset. This time around, you shouldn't just aim for the degree, you should be aiming for the learning. Do not aim for promotion, aim for knowledge that can make you an indispensable worker. Mastery can avoid your work from dictating your life. Not everybody gets this freedom.
The quest for a few extra letters after your name should not be an easy one. So the next time you catch yourself in front of a professor asking you to write essays about Life (as you know it), waste your time on college-type presentations, or irritated at questions, think twice or demand for your money's worth. Choose a good graduate school with good (industry-experienced) professors who develop good syllabi.
This goes for short professional courses too. I wish you the best of luck.