Keep at it, m'dear. The rewards are worth the reaping. When I was doing my doctorate they had it structured so you were taking one class at a time and it was condensed into 8 week modules so I know what a drag it is to have multiple hours every night all in the same subject. It's not like you can put it aside and say, "ah hell, I'll do a little Calculus for a while" or "think I'll pick up that novel for my literature class and read a couple chapters". Nope. You're stuck in the mundane. But it REALLY REALLY will come out fantastic in the end.