One of the problems with friends is that they think they know who we are. They're used to us; they see us day in and day out, or every week, or we call each other all the time, and - you know, I don't want to say "familiarity breeds contempt", but that's nudging at the inside of my skull. It's not contempt per se that's the problem, more a supposition that the accustomed is the actual. That what one is used to seeing is actually what there is, and all that there is, in there.
You become to them a stereotype of yourself. They expect you to live in the territory that is approximated by their crude map, and not to stray beyond its boundaries.
Sometimes we buy into these caricatures of our selves, too. In some ways they make interacting with people much simpler. Each person becomes defined in terms of a limited set of interests, a small repertoire of discourse, a cluster of habits. We know who is "the one who takes things a bit too seriously"; "the joker"; "the agent provocateur"; "the shy one with a kindly heart". I suspect I'm not the only person who can come up with ten-word (or fewer, even) capsule descriptions of nearly all my friends. As mental shorthand, they're convenient. As expectations, as limits to place upon people, as borders to be patrolled and maintained at all costs... no.
Do not project clichés about yourself; people will believe them, and will react strangely and counter to your hopes if you try to move outside them. Do not believe clichés about others. Most importantly, do not believe them about yourself.