Software project estimates are too often wrong, and the more time we throw at making them, the more we steal from the real work of building software. Also: Managers have a habit of treating developers’ back-of-the-envelope estimates as contractual deadlines, then freaking out when they’re missed. And wait, there’s more: Developers, terrified by that prospect, put more and more energy into obsessive trips down estimation rabbit-holes. Estimation becomes a form of “yak-shaving”—a ritual enacted to put off actual work.
I tell them to turn to the study of mathematics, for it is only there that they might escape the lusts of the flesh. -- Thomas Mann, "The Magic Mountain"