The burn-out happened to a major degree at my last place of employment. I was an early employee at an electronics startup and I was working around 17 hours a day migrating an early version of the web application from PHP into Node, programming arduino and raspberry pi boards, adding various payment modes to an android application, and writing server code in Haskell (a language chosen for no good reason other than it sounded cool and nobody except me could even read the code, the person who wrote it initially having left). 10 months of this ultimately took its toll.