Derrick settled quickly into the lifestyle of a servant. He existed to make his Centaur happy, and took pleasure in everything from brushing and grooming to scrubbing troughs, buckets and stall floors. The dulling of his mind eased up somewhat, and after a few days Derrick could remember and reason mostly as well as ever. Two things became apparent - the other stable boys were probably not former guests, as they did not show any signs of higher intelligence. More importantly, something had changed in Derrick's mind, as serving the Centaur was just as pleasing despite memories of his human past. His life was total selfless devotion to the half-horse being, with no consideration for himself. As a human teenager, he had been spoiled, selfish, and lazy. It was strange thinking of all the time he had wasted playing games, watching videos, texting nonsense. Never satisfied, never content.
Deep-down, Derrick realized that whatever had been done to him had altered his basic personality. Before they came to the resort, Derrick would have rebelled at having to do daily chores, let alone live like an animal himself. Now he looked, acted, and lived as a servant beast, or perhaps more a working pet. His Centaur was kind and gentle, forgiving of mistakes and quick to praise and show affection. A rub of the chin or stroke of his face and shoulders was enough to make a whole day's hard work more than worth it.
This new lifestyle became so normal that Derrick was actually confused for a bit when his Centaur stopped him after a grooming sessions and said "Your time is over. You are due to return to your family and your old way of life tomorrow."
Derrick trembled and dropped awkwardly down as low as he could. "Master, have I done something wrong? Have I offended you somehow? Why must I...?"
The Centaur lifted him up with a firm hand under his chin. "Think, remember. Your name is Derrick, and you came here as a human two weeks ago. This has been your choice as a vacation - your family allowed you to remain here since you were obviously happy. But the vacation is ending, and you are supposed to return to your 'real' life and form."
Derrick struggled with the conflicting identities in his head. If he went back to being Derrick, he would have to be the pale, hairless, weak human who lived in a world of useless technology and 'friends' who rarely looked up from their cell phones. No - there was more to his old life than that. He had school yet, and a a future where he would get a job, maybe have a family. Yet he doubted that any future as a human would hold the deep satisfaction and contentment he had experienced over the past two weeks. "My Centaur, do I have to go? Do the stableboys always have to leave and return to their old lives?"
That made his Centaur chuckle. "No guest has ever chosen to become a stable boy before. Many have become centaurs, some have become horses, others just wanted to have sexual experiences. Only you have taken the form and lifestyle of a stable boy. Yet you have been perfect. I would ask you to stay with me forever."
"So I have a choice?" Derrick felt hope and uncertainty war within. "I could remain here as a stable boy? As your stable boy?"
"It would require permission of your family and such a choice would not be reversible. You remain different from your fellow stable boys, with more intelligence and reasoning than you need, and memories that belong to your old life. If you choose to stay, those would all gradually fade away, and you would be mentally unable to be anything but what you have been the past two weeks."
That didn't sound so bad to Derrick. Yet enough of his old memories remained that he knew he would be giving up a lot of comforts, and lock his potential future into that of a slave. This desire to please, to serve was part of his change - that would probably change along with his body when and if he became Derrick the teenage boy.
His Centaur stroked Derrick's cheek. "You must decide now, for the process to become human will take much longer than it did becoming a stable boy. And convincing your family to let you remain like this may also take some time. So either way, a choice must be made."