Here is something I learned in college: Give yourself one day off a week. I found that no matter what, there was one day a week where I didn't get anything done. Make the most of that day, and plan around the idea that you only have 6 days to get things done. It's easier to spread out your work into that day off, than it is to recover from an unexpected lost day. Also, if you want to go out one evening, don't make that your day off, make the next day your day off. It's the day after that hangovers/late nights in general get you.
Also for workouts, some very effective workouts only take 30 minutes. They won't get you ready for the olympics, but they'll keep you in shape. No one can't find 30 minutes 4-5 times a week. However, that time might come out of your "3-4 hours a day", so you may need to consider whether or not browsing the internet/reading books is more important than your workouts.