If you are tired, cut back on your studies until you find a manageable load. People who are working full time should have part time studies. To try to do both your work and your studies will most ofter result in one of the two not being done well (it's usually NOT work that suffers).
If you are working nights, you need to figure out when you are most alert during the day. When I was a RRT working night shift, I was most alert in the morning after I completed my shift. I scheduled all of my classes in the early AM and slept in the afternoon.
You may also try to get some aerobic exercise in on your lunch hour at night. You could walk a few flights of stairs at that time so the your blood keeps circulating. Arrive at work early and do a few flights then too. You will find that you are more alert and more efficient.
Working night shift goes against your circadian rhythms and makes most people feel tired. Wearing sun shades in the day and darkening you room when you sleep will help but you need to take your time with your coursework and schedule your courses/study time when you are most alert.