A fun word floated to the top of my head today: Wabi-sabi. It's Japanese, referring to an imperfect, transient melancholy, basically the mood I get into every October around this time. The Wiki on it is pretty good but here's a moment I think defines the word for me:
I was walking back to my apartment where I lived for a year in Japan. I turned a corner and saw this flash of red pass in front of my eyes. A red butterfly, seized by the wind. I froze, watching it flutter down to the sidewalk in front of me. Touching ground it became a red momiji leaf.