This is where I was at this time last year. I lost motivation for further because it was just boring me. Short answer is DON"T!. Seriously though, every little bit counts in further. A couple of marks could mean a couple points drop in study score. Further is easy but there is tricks that get people. Just think there is also other smart students out there taking advantage of the "further situation" who are studying right now, right now those who you are competing with.
You have to stay to yourself, it is only 3 more weeks then I can forget as much as further as possible and "burn the books". Once these three weeks are gone you can't get them back, use them. And there is always plenty of time for the fun meth and spesh stuff on the holidays, when you are less stressed, you are mroe relaxed and will be able to enjoy it more.
Say this out loud to yourself. "I am going to do the best I can in further. I am going to put all my effort into further for the next three weeks. I am going to go and ace those exams."
Also remember small silly mistakes cost you a lot in further, time to iron those out now.
Don't get slack like I did, you'll drop that little bit to a 45 like I did (not that that is bad, I'm happy with that, I'm just sayong if I didn't get slack maybe it would be higher).
Good luck.
EDIT: Remember, don't die from overdoing it though, you need a rest sometimes.