At the risk of offering some rather generic advice, it's fairly safe to assume that an MSc in physics is going to be quite demanding on your time. The specifics will lie in the details... how many courses you take each semester, how strong your background is in each course, what your teaching responsibilities are, if it's a research MSc what's expected of you in relation to your project, how good you are at managing your time, etc. As a general rule I think you can expect to treat it like a full time job. The majority of your days will be filled with classes or work related to them, but you won't be without down time. Academic programs are not designed to eat up every waking minute of a student's time (if they are, that's not a healthy program to be in).