> Learn when you can't code anymore. Learn when you can't process things anymore. Don't push beyond that, it will just make things worse in the future.

I cannot agree more. (18 years developer here). On those days I just kept pushing, I mostly ended up correcting my poorly-created code the next day. When you know you're done, be done, or at least switch to the lowest mental energy task you can do. Sometimes staring into the screen is that lowest mental task.