I don't have much advice, but lots of commiseration. I tried to drop out every single semester during the first 3 and half years of grad school, then during the dissertation, well, got that far, might as well finish. But 10 years later it has paid off, now I can do triathlon training fairly intensely cause I can organize my own class hours and student hours and research hours, unlike most of the working world, and THAT COUNTS for an athlete. While training for my first tri I kept telling myself that if I could write a dissertation, I could certainly do this, and during the "book" stage, I kept telling myself that if I could do a triathlon, well I could finish the book.