Pretty much feels like a second job to me and currently in the stage of advancing in my career and learning Rust on the side and more devops things and then the actual job as a Java SWE I already do like a 150%/60+ hour week, I can not have a 250% load.
There are phases of life where it makes sense to prevent preoccupying yourself with romantic relationships (which end up occupying large chunks of your free time), however I believe that long term this is a bad strategy. Focusing on career above all else will not make you happy in the long run unless you define your entire identity as a career professional.
In short bursts this is probably fine (and I followed a similar strategy early in my career) but I am personally happy to have not fallen into the trap of focusing on my career to the detriment of my personal life throughout my entire youth.
Well, no-one can decide your priorities for you, but this is a path you want to be sure you want to follow, as your life options narrow more quickly than you might imagine.
Advancing your career may seem important now, but will you feel that way on your deathbed looking back?
