Grief
It is like a broken song playing on repeat in your chest, almost like a bird who doesn't know the way out and is crying hauntingly to be free. It's the feeling of watching the sunset and getting an ache that echos in your chest when you wonder if this is the last time you'll see it. It is the shattering of trees in the winter and how beautifully saddening it can be. It is hot tears that cause mind-numbing headaches and runny noses that make us wish we can just breathe again.
It can be anything and everything at once, because in all things there is this feeling, even if not felt by you because even that beautiful willow tree that you see every day on your way to town hides a deep sadness, and it mourns the loss of the forest that once stood around it.