Your work reflects on them. Your wonderful work makes them look good and actually gets the role cast. Your disconnected, tentative, muddled work does nothing for anyone. They need you to be great. They’re here to host your experience and shepherd you in, not hold you back.
They want to share in your excellent work. It gets their job done. And most of all, it makes them happy! It's what they live for. Whether it’s a pre-read for an associate or a full-blown director/producer callback session (or a self-tape you do on your own), this is your time, your experience. This is your opportunity to do exceptional work. Enter the space and do the work for yourself, for the gratification and love of the work itself, and to collaborate with the other creative people waiting to figure it out with you.