I wonder what jalmy8 thinks is on the other side...
The first thing is that this exam shouldn't really take 4 months of intense studying. According to CFAI, the recommended number of hours is about 300 hrs so 4 months is about 2 1/2 hours a day. This is a significant commitment for sure but an hour a day on weekdays, a full day on Saturday and a half day on Sunday should do it. Many candidates pass on significantly less work than that. If you are doing lots more than that and failing, there's either a studying problem or a background problem. If it's a studying problem, AF people can help with all kinds of study suggestions. Anyway, step #1 to avoid burnout is to study efficiently and well so it doesn't consume lots of time.
Location - where are you studying? I think studying amidst distractions can increase burnout by forcing you to work your brain hard balancing and screening distractions while studying. I used to check into hotel rooms and study there from check-in on Saturday to check-out on Sunday with a nice night's sleep in the middle. That helped me avoid distractions of kids/wife, phone, etc. and I got tons of productive study time. I actually looked forward to doing it with my ritual 10:00 PM order of wine and dinner from room service and some movie on Pay-per-View (no, not those movies). The hotel (I liked the Westin which has cheap weekend rates) would set up a conference table in the room for me and I would spread out my books everywhere. Try it - it's relaxing and kind of fun.
Exercise is important. Lots of folks complain about floppy biceps and guts after their exam. You probably shouldn't schedule any fall marathons before Dec. exam, but dropping it altogether is a bad plan. Everything I've seen on light exercise says that it is good for all kinds of mental functions as well as fighting burnout and stress. Since your social life is going to suck, I think you should combine social life with exercise for time efficiency and maintaining some friends. Run with your buddies, play basketball, or do whatever you do.
Mix it up. Don't go through the material linearly. Study what you want whenever you want. If you feel like studying derivatives, then do it. Sometimes some really natural thing comes up, say from an interesting question on AF. You should go study that because you want the answer. You can get tons of studying done that way without feeling imposed upon. It's also much easier than sitting down and saying "I have to read FSA yet again, darn it".
Study with a partner sometimes. This is not the hot babe who works in the mailroom. This is a motivated group that is fun to be with. Joke around with them. Make every Thursday night the time you meet the guys at UBS to study and then have a quick beer afterwards (my plan for L II years ago). This adds another dimension to your studying in which you teach the stuff to someone else. You learn things very well doing that.
Get your wife on-board. If your wife is really stressed about your studying, it will suck. There is nothing worse than feeling marital pressure and thinking your marriage is going down the tubes for a stupid piece of paper. As someone with an ex-wife and a CFA charter, I am absolutely certain that a good marriage is way, way more important to life happiness than a CFA charter. This stress will eat you alive and really increase burnout if you don't get her help and permission. It's also really f-ing dumb. If the quest for a CFA charter is eating your marriage, just don't do it.
Time off. Even God rested one day out of seven. Break one minute out of seven, one hour out of seven, one day out of seven, etc... Rest time is as important for developing as study time. This part is the same as athletics - your brain is not that much different from your cardiovascular system or your pectorals. If you want to develop it, you need to let it rest sometimes too.
Do not waste lots of hours on AF. Very bad.
