Staying on track was very important for Mark. All eyes were on him and how he performed.
He had with great effort taken control of his life, which was previously getting away from him like a runaway train. No more drugs, no more wild parties, he had sworn off them and had cleaned up his act. He had to show his father that he was the responsible adult that he proclaimed.
After all, he had no desire to lose the family millions to strangers, which his father had threatened him of doing! In fact, he was enjoying the new lifestyle so much that it had become real for him, instead of the show that he had been putting on for his father.