I had a job this summer where I either worked 5:30 a.m. - 1:00 p.m. or I worked 6 p.m. - 2:00 a.m. It was absolutely dreadful. My week went like this - Monday and Friday and sometimes Sat./Sun., morning shift. Tuesday, Wednesday, night shift. I learned to accept it, but it basically ate away my social life.
The job was meaningful (U of M Dept. of Public Safety) but a lot of it was downtime. I liked what I was doing, but the hours were horrible. I learned to sleep BEFORE work, rather than after it. I napped during the day. I got to bed early. Sure, my job was temporary (summer work only, now I have a job with perfect daytime hours), but you too can learn to accept it. If you do something meaningful while you're working (read classic literature, listen to good jazz music, learn a foreign language, write your great American novel, etc.) you'll look forward to going to work.
The key is not to like what you're doing, but to look forward to your job. Obviously you hate what you're doing NOW, but since you have so much free time, change what you're doing...make work fun for yourself! 🙂
Good luck.