I am doing do a degree and paying the bills by freelancing. So 50-60hr/wk, combined education and work, is something regular.

It is possible to sustain it, if you are an introvert like me. It's just important not to do the same thing all the time. My degree is focused on low level programming and hardware, and I mainly do AngularJS development for living. So this kind of switch definitely helps.

Other thing which is important, at least personally, is that when you take a break, you must do something that counts. Browsing internet just drains more energy, personally. But I find playing an action packed video game (if you can't bother to go outside - or if you live in North England like I do) quite recharging. [0]

[0] I wrote more about that in my blog http://blog.gedrap.me/blog/2014/02/09/its-all-about-the-shor...