I, too, was a full-time student with a full-time job, so I understand how difficult it can be to balance your work, school, and personal lives.
You are right in thinking that both your job and your studies are important. In some way, one relies on the other for success. Since you can't give up either one, you have to make sacrifices in other areas of your life.
For example, when I was in school, I pretty much gave up my social life. I never saw my friends, and I rarely saw my family (even though they live close to me). I hardly ever went out. When I did, it was only because I was caught up with my work.
This is not to say that you shouldn't allow yourself room to breathe and take breaks. If you push yourself too hard for too long, then both your job and your schoolwork will suffer. The point, really, is that you're essentially working two full-time jobs (because you have to look at school like a job), and these jobs must take priority over most other areas of your life. The key is balance. Don't let one area of your life dominate another for too long.
It may also help you to constantly evaluate and reevaluate your processes. As you progress in your studies, you will come to recognize what works for you and what doesn't. Maybe you find that it's very difficult to write a paper after a long day at work, so you choose to work on big projects on your days off. Don't be afraid to make mistakes, but make sure to learn from those mistakes. If one kind of approach doesn't work, try another. The process of learning involves experimentation.
I know this response is pretty general, but hopefully you find some pieces of it that can apply to your specific situation. Good luck. You have a hard road ahead of you, but with dedication and planning, you will succeed.