I experience these points all the time. There are small ones that happen daily or weekly, like doing the dishes—the point where I've dug through the mound of cups, bowls, plates and the nasty pots remain. That's the point where I just want to stop and be done, where I feel like I've worked enough.
I remember this point well in college, too. The point when I'd gotten too far in to back out, but not far enough to see the end, and I just wanted to hide in a hole and not face my plight. And of course there's that point in pregnancy, where you just want to be done but you have 3 months left and WHY? Or when running, when you hit that wall where it feels like you want to die rather than take another step.
Of course, there are many of these points in writing as well. I feel this way frequently when I write a first draft or revise, when I must wait for whatever comes next.
And the sad thing is? This point is usually more near the middle than the end.
This is the truth, and yet I always want to think this feeling means I'm almost done. Perhaps because when I get a case of "Can I be done now?" I start to rush. I get antsy and careless and try my hardest to convince myself there's not as much work as there is. I begin to look for short cuts. But short cuts always come at a price, and that price is usually more work in the next phase. You can never escape the work.
One of the hardest lessons I've learned is to resist the "Can I be done now?" feeling. It's hard to do, especially when you have been working so hard for so long, and all you want is to be done but the REAL done is so far away. I have to stop myself from getting hasty, accept that I still have a bunch of work ahead of me, and then find a way to do it with some measure of cheer. In the end, when I've done this instead of rushing forward in an overwhelmed, maddened flurry, I've seen the result I'd hoped for. When I haven't, people usually tell me I have more work to do. Go figure.