Work harder and feel motivated

Hola viners

My existential thoughts are kicking in and I am mid 20s, wanted to know from y’all ,what it looks like to have a 12 hr or more workday. Is it possible or have you done/seen such kind of work which let’s you constantly focus and be productive straight up for like 12 hours. Can you be that monotonous. My system just shuts down in like 1-2 hr and all different life anxieties start kicking in🥲.