Why did you do it? What made you decide to go to grad school in the first place?
Ok, take away all of the reasons like "I want to be a professor", "I want to make sweet professor cash", "I want to have tenure one day so that I never have to worry about getting fired", etc.
Boil it down to some tangible act that you enjoy performing (hopefully there's still something there, or you might have a problem). What made you love your subject so much that you decided to spend the next 40-60+ years devoted to exploring the most minute details of it? Try to remember that.
Now, let's try to get back to that.
Obviously, you can't completely ignore the parts of the program you dislike, but if you can remember what you did love, and make a concerted effort to introduce that back into your daily routine, then those other things that are causing your PhD Depression just may become bearable.
Personally, it might sound crazy, but I didn't start the program for the research or teaching aspect. I started it because I enjoyed the course work as an undergrad. Being a good student, I had gotten the opportunity to work on a few research projects, which I thought were representative of what I would be doing. That was not the case. I know now that what the undergrads do in my field (engineering) on research projects involves much less open-ended research, and more implementing of a nicely defined concept (which is similar to undergraduate course work).
It was a rude awaking to find how open-ended and ambiguous real research is. I can get very overwhelmed by this ambiguity, which makes me want to crawl under the covers and ignore the world.
But lately I've been trying to set small daily goals of working on the concrete implementation of concepts that I enjoyed as an undergrad, and it has reignited a little of my passion.
So try it out. If you can allocate a small amount of time to whatever it is that you loved doing with your subject, can it make the rest of the day and drudgery bearable? Let me know how it goes.