What can explain the fact that I'm alert and ready to face this day?

On Mondays I work a 12 hour day, from 8 a.m. to 8 p.m. Then I have to get up at 6:30 a.m. on Tuesday to work a regular 8 hr day and on through the week. Needless to say, I’m am dragging and dog tired after work on Monday, with almost no time to decompress before I go to bed. I started this three weeks ago, with a Monday off for Labor day last week.

Last night I’m so tired I’m almost hurting, not only because of the 12 hours, but because just before closing I actually got sick…it was the lunch I had at 4:30. Just a burrito but for whatever reason about 7:30 it decided it wasn’t going to stay down. I kept telling myself to be in bed by 10:00 last night….but I kept putting it off and putting it off, and didn’t go to bed until after 11. That means less than 8 hrs of sleep (left to myself I can sleep 11, 12 hours easy!) I fully expected to be dragging, half dead and irritable this morning like I was the two other Mondays I worked even when I hadn’t gotten sick…but I wasn’t. My alarm went off, and woke up easily, got out of bed and faced that day feeling well rested and relaxed.

How can that be? Am I imagining things??