Been there, done that. It isn't a happy place to be. My best advice is to keep it simple. Knit easy things that you can finish quickly. Look for small victories to pursue in other areas, like cleaning out the junk drawer. Watch your old home movies and go through the scrapbook to remind yourself of better times. Keep the faith, whatever it may be. Get some quality exercise every day. Take your vitamins, eat right, and get plenty of sleep.
When I have an ordeal to get through, and I don't know how long it will last, I keep track of how much of it I've already gone through and take some comfort in knowing I'm that much closer to the end of it.