40 pages seems dautning in your position, but it's not so much actually. Chunk it down. If this is possible in your field, lay out the structure, write down the names of the paragraphs (even you remove them later) and then just tell yourself "ok, I think today I can do 10 minutes, I'll fill up one paragraph". In very small dosis it can work better. Who knows, maybe on that day you'll actually do two paragraphs! And like other said - don't quit now, you're soooo near the end, you can power through it! If you combine all tips - ask for a few hours less + power through + chunk the thesis - I'm certain you'll manage! Wishing you the best of luck.