Circadian Rhythm

Today I am so thankful for the Circadian Rhythm.
The Circadian Rhythm is a body response that regulates a series of basal actions, including the sleep cycle.  Despite my three years of a science degree, I don't remember a whole lot about the Circadian Rhythm, but I know that part of it is the body's "internal clock."
And I am so thankful.
I've been working a lot of evenings recently, and I had a night shift Wednesday that I haven't fully recovered from.  I've also been working every day, many hours a day.  Plus I'm entering the last weekend of a course that I'm taking, which is really stressing me out because I haven't had the chance to do all my work yet.  I still have a few things to study and 15 pages of a paper to write!  I am really paranoid about the paper, but I'm also exhausted.
I'm trying to fight the Circadian Rhythm - I have been trying to do so since I got off work at midnight on Tuesday and then when I stayed up all night to work on Wednesday.  But I'm so tired.  I'm so tired, and I have to work tomorrow morning.
I crave sleep.
Thank you, Circadian Rhythm, for reminding me that sleep is good.