Work harder and work smarter than everyone else. Take everything seriously -- we've been training doctors this way for decades and while it's not perfect, it seems to get the job done and I certainly don't have a better way.
Beyond that, keep your eye on the prize. An attending mentor of mine put it this way: From now on, your life and career will be a mixture of clinical practice, reading, study, exams, BS assignments, paperwork, family time, relaxation, etc. The only difference between you as an M1, an M3, a PGY-2, a fellow, and him as an attending is the ratio of each part to the other parts, plus he has a nicer car and a bigger house. Otherwise, it's all one big continuum. Keep that in mind and let it inform your mindset and your approach to the work.