Chameleon

Sometimes i really don't understand human multiple manner.
For example the friendship.
One day we are friends, but the next day we are not.
Why people change their character so easily like a chameleon which changes it's color in every environment?
I can't say that i am a good friend. Someone could say
"she's so selfish" or "she is very kind". So, which is my real character?
From this view, i am also a kind of chameleon. Furthermore everyone is a chameleon which has a different color. But it should be balanced...