I notice this most often during my Wednesday church choir practices. It didn't take long for me to develop a bit of a reputation as a goof-ball. Thankfully, my director is a fantastic, good-natured person who usually deals with my antics with good humor (such as mock-seriously asking my mother, who is also in the choir, to "control her son"). I like livening up a group and getting to see people smile, and sometimes even laugh to the point that they're crying.
While I try to bring levity with me to any gathering, when I'm tired it's almost effortless. When fully rested, I sometimes notice that I am trying too hard to get that smile or laugh. Yet when sleep-deprived, the witticisms seem to pop up naturally.
Now, I would still prefer to have more sleep, but at least there seems to be a side benefit. Unless ... being tired just makes me think that I'm being funnier ...
Nah, I'm hilarious.