upset song

That song suddenly just randomly played inside Itunes

I found myself inside that song

that song without a title, without lyrics

It is my upset song,

today has a unwritten emotional and stirring inside

something not really right inside and outside.

I wonder why "upset" but not "upsad"?

P.s: I remember i said this when I was small:

"等我长大以后,我要到一个很远很远很远的地方."