Half full. half empty

Have you ever experienced the feeling that you have done everything but at the end of the day, there is something missing. The feeling of longing for someone or craving for something that you can't really identify whom it is or what it is. The feeling that you're almost full, but deep within, you're your empty.

I can't find the right word to describe it. It is hard to explain how does it feel but for sure it sucks, totally sucks.