If you do what you need to do week by week, you should have plenty of time to both study and play arma. Also, If you don't have a job, you shouldn't have much issues at all, unless you are in your 3rd/4th year of engineering school or something like that.
If you don't want to be too busy during your semester and have better grades, cancel a class, and do it during the summer if it's available (unless you have an internship), or if you don't mind doing an extra semester, do them during that extra semester.
It's all about balance, planning ahead and discipline.
Your future employer will prefer somebody with near/or straight A's that took an extra semester to complete his major, than a straight B and sometimes A student that completed everything on time.
You don't have to completely quit arma for 4 months, you'll be able to squeeze a few hours per week, and you won't get a depression. Obviously, study harder a few weeks before your exams and leave arma for the time being.
Also, the amount of study required varies between students and their goals. Figure out yours and look from there.