People always change, and Cui Changxiao dares not guarantee that he will never change in his lifetime. When he's older, his way of seeing things and landscapes, and his thoughts will certainly be different from now, owing to more experience and the insights accumulated over time.
Just like now, he feels that he's become less impulsive compared to when he was a teenager.
So he actually quite understands the changes in Song Zhiyuan's temperament—it's simply due to more experience, seeing more things, having heavier burdens, and thus approaching matters with more calmness and handling them more smoothly. After all, a slight move can affect the whole, and one cannot act rashly.
Impulsiveness is left for the inexperienced youth.
One more thing he hasn't mentioned is that because Song Zhiyuan has been an official for a long time, he has turned into a seasoned veteran who knows very well what it means to be close to the Emperor like being close to a tiger.
