When I attempted to describe to a friend what I meant by "you are who you are with" the first response was "I try not to be different. That would mean that I'm a phony at times."
No. What I simply meant is this–we are different with different people because it is our relationship with them, our feelings towards them, and a variety of other factors which produces what is unique to that relationship.
You are not the same person in your relationship to your spouse that you are with a friend. You are not the same person when dealing with a business partner as with a relative. You are different in your dealing with your parents, and each parent is different as well.
You speak to each friend and relate to them each differently.
If you have children, you are different with each one.
Much of this difference reflects the nature and personality of the other individual and how you feel towards them.
In other words, the relationship determines how you speak, act, behave towards the other. Usually we are not aware of this. The interaction occurs spontaneously without conscious thought.
In many cases the differences are quite subtle. But I believe they are there.
What adds to the confusion is that as these relationships change over tim. So do we when we are engaged in them. When you are angry with someone, you are different towards them. When you reconcile, again you are different. If you find someone attractive on any level you relate to them differently than someone who "turns you off".
We "read" the other's feelings, intentions, emotions and are guided in our own responses by what we perceive. Much of this, on a subliminal level.
In fact some autistic, Asperger's individuals have difficulty with interpersonal relationships because they do not "read" others very well. In other words, they often fail to establish flowing, harmonious relations with others. They may not "change" from relationship to relationship as most of us do.
So don't be hard on yourself if you notice the phenomenon in yourself. You are not a phony. Just human.