Blue.

Feeling blue.... That mix of feelings between sadness, melancholy and  depression .... 
You are not happy in full. You are not sad in full.... Too lazy to walk... Top lazy to talk.... You are not crying. You are not smiling.
I call it blue.... Just blue...
So I sing.

Adele - Chasing Pavements

Christina Perri - Arms

Adele - Set Fire To The Rain  

Eminem - Space Bound

Rihanna - California King Bed

Amy Winehouse - Tears Dry On Their Own

Lil Wayne - How To Love