Who Are You?

The question is: who are you?

I've mostly been wondering are you the social you (the you that everyone sees and interacts with) or are you the private you (that only you know)?

Or can you be a combination of the two?

Can one person have two opposite parts (if the social and private yous are different)?

Can I be both happy and depressed? It seems you would have to be one or the other.