I remember the very first time I encountered this.

I was crying over the final of american idol. someone asked me why are you crying at american idol?. you don't even watch it, and the contestants are singing happy, uplifting songs

but I couldn't respond. I just knew I was sad, and it lasted all evening (even problems eating because of it)

over the years, I think it's got better (I now mainly cry at trivial things)

but this still happens ocasionally