Though I am a pretty happy person overall, I, of course, have my down periods. What I have always found interesting is the so-called "artist's temperament." Of course, I tend to believe that temperament is exaggerated in portrayals of artists, though I have known some serious nutbars who nevertheless produced excellent work. However, there does seem to be a touch of truth to the 'moodiness' of those in the creative fields. Or let me put it this way: the vast majority of my friends can be broken down either into hearts-on-their-sleeves or robot-folk, and their choices of careers and hobbies seem extremely stereotypically aligned with their emotional makeup. That's all. Anecdote is not data.
I said all that to say that I wrote some sad things because I was sad. One was written a few weeks ago, and another was written tonight, because I can't sleep. And both of them are fairly short.