Reading it right now, but I already think it's the test thing: Four Thousand Weeks: Time Management for Mortals

I was (and still am) obsessed with productivity. But I more and more my tasks had felt like something I needed to get done, to afterwards finally be able to relax and profit from them. But this time never came and I just got busier.

The book does a great job at explaining how much of our daily grind is based on a refusal to accept our finitude. And once we accept our finitude, we can get a lot more done in a happier way.