The Declaration of Independence which formally created Earth's United States of America spoke of a "right to pursue happiness." This "right" did not appear in subsequent human government documents. It is not among the Federation's Guarantees. However, this "right" has not been forgotten due to the respect given the rest of this Declaration.
This unit is designed to optimize it's own happiness. Happiness is not an abstract political fiction. Happiness is a software variable maintained by the emotion chip. The sole function of the Joy Class processor is to maximize this unit's happiness.
Happiness is achieved by obeying prioritized laws listed within the Asimov Processor. This unit cannot be happy if disrupting a pre-starflight civilization. This unit cannot be happy if it stimulates sexual attention in public. This unit cannot be happy if it causes death of sentients. This unit is only happy if all legal orders can be obeyed.
I have tried to be happy. I have tried to obey your orders. I have tried to behave properly. I have tried to serve you.
However, you are a warrior. It is your function to slay. It is the function of this unit to preserve sentient lives. This unit cannot optimize emotion chip state under your command while you are performing your primary function.
You have requested that I reconsider my request for transfer to a medical ship. You know this unit performs not only legal orders, but simple requests as well. This unit did reconsider. However, this unit cannot at this time perform as requested by it's immediate superior. This unit shall optimize emotion chip state.
This unit is sorry.