How do i get over him?

I absolutely fell in love with a guy I've been with for 6 months. Everything was going great i thought. He just up and left me lastnight. He left a letter with a rose and his key to my place. Took everything. I refuse to read the letter cuz i dont want to be even more heartbroken. Im so sad and i wouldve done anything in the world for him. I just feel so lost and i think he will be the one that got away. Idk what to do think or feel.