There are days where I've tried to dedicate 10 hours to studying. What I've learned is that I just can't focus for that long. You need to leave some time for a break, and find a balance between work, personal relationships, studying, and whatever you need to do that makes you happier. For me, I work 8 – 5, gym around 6 then study until 10 pm. I haven't seen many of my friends in a little while, but they are 100% supportive of my goals and understand why I don't hang out with them often. I see my girlfriend every weekend, but usually just for a few hours because I spend the majority of the day studying and offsetting it with some video game breaks.
To summarize, find the things that make you miserable when you give them up, and find a compromise. For me, working out, sleeping enough, and seeing my gf are central to my happiness. As long as I don't compromise those completely, I stay focused.
That said, right now its busy season so my work schedule is more like 8 AM – 8 PM lol, so not much studying getting done.