Can I tell you that this ^^ is word for word how I feel often, and DAILY for probably 2-3 months straight, before that it was recurring for the past 4 years working here (5 years in Oct).
I will tell you first hand, it will not get any better if you do not try to fix it. Adjust your mental focus to get in get out get work done, nothing more nothing less until you get to leave or find another job. You can see the unhappiness in your face even though YOU can't see it, others can. Stay positive, I try to do this everyday and phuck if it ain't the hardest thing, and I don't always succeed b/c some jerk tries to ruin my day.
I have no clue how I'm going to last another ~ 3 years here, my sanity is already questionable, but I need to do it. I have no other option at this time.
SO hang in there, BREAK the pattern of the negatives, and is you wanna sleep all day & do nothing for a few days & cry? FINE do it, get it out of your system, then turn to the next chapter ...