How do you tell the difference between discipline and running on empty?

I've been translating a 90-page technical manual for weeks and I've hit this strange stretch where the deadline feels real but it's stopped motivating me. Not panic, not focus — just a flat hum of obligation. I'm starting to wonder if this is what discipline looks like from the inside, or if I'm just coasting. Does anyone else know the difference, or is it only visible in hindsight?