Not for long. People feel like they're really getting to know you if you're that caged off.
You can be genuine without being emotional
Most of the successful people I've seen in my career had a demeanor that ranged between "happy and pleasant" and "serious and stoic". Founders and top executives can get away with being passionate (e.g. Steve Jobs) but serious, reserved stoicism seems to be the norm (e.g. Tim Cook).