A Lab Technician's Woes

Summonned into the Boss's room I stood firm and answered: "I am only trying to do my best". 

Visibly enraged he retorted:"Your best is not at all good".

Trained to be irreverent I naturally rose to the occasion: "So from my worst you make your best".

Frowning he collected his briefcase and stormed out of his own room leaving me alone, and intact.

How come we become less professional precisely when it is expected to be the other way round or rather the other way up.