Burnout.
You can ask your body and mind to push through and, despite needing rest, they will trust you and do that. The deal is that after the push-through, you take a break and help them rejuvenate.
When we have an external boss, it's easier to negotiate a vacation. We find it easier to forget our laptops at home and put our phones in offline mode.
But when we are our own boss, it's easier to keep pushing through.
It's a trait of a professional to schedule rejuvenation time much before they put anything else on the calendar.