When I attended college, I took a full course-load, worked 30-40 hours per week and was involved in a sorority that was very active in volunteer work. It was crazy hard but worth every moment. I think the key is to be present where you are. When you are in class or studying --you are learning, you aren't worried about your work schedule or your extracurriculars. Same deal for work, when I worked, I was working and not thinking about school or extracurriculars.
I sought balance many ways-no step was more important than another step:
1) Making sure my employer knew my course schedule. I made sure to complete work shifts in one segment that was after or before ALL my classes or on weekends. I didn't split shifts. I tried that and it was chaotic.
2) For my extracurriculars, I made sure I only committed to events where I could be totally committed. So if there was a sorority volunteer event that would overlap work, I would forgo that opportunity and chose something else. The sorority knew my course work load as well as the fact that I was working full time. They appreciated the fact that when I was in attendance, I was fully engaged.
3) I used a calendar to make sure I blocked of study time (individual and group) per class so I would make sure I chunked it out and avoided "cramming" for any test, paper, lab etc.
It was hard work. It helped me improve my organizational skills --which you need in any job. It also, taught me how to keep a healthy work/life balance over the years. Most importantly, it was great practice to be "present" in whatever situation I find myself.