Character is what we answer to. If you answer to some thing less than what you are you are then denying your true self. A more notable Cliche says "character is what you do when no one is watching". This is true but character is a lot more than that. It is the way you allow people to talk to you. The company that is kept and the way you think also are what drives character.
The company kept is a pivotal feature of character because they are your growth rate. Your growth rate as an individual is complementary to what you know and what you learn regularly. If the people you are tied to do not uplift you then you are denying yourself of moral responsibility to live life. Thus your character is is now questionable.
You can be around these people in public and act like them in private. You are then not being morally irresponsible with your character. You can then at this point lose your natural identity and then become someone else character. Character is claiming the highest aspirations and moral "uprightness"!
Character is daring to be a gentleman in a world that harsh to women. Character is daring to treat your naysayers like the king you are. Character is determination. Character is waking up in the night before a game to watch film because you refuse to lose. Character is helping a homeless person eat. Character is looking out for family even when they are not the best example.