To be honest, Prince An couldn't understand Pei Ji'an.
People say he's young yet already famous, achieving feats others might not accomplish in their entire lives or even in several generations. Plus, he's a powerful official; truly, every accolade seems to belong to him.
Moreover, he just recently earned another triumph and got rewarded by the Emperor, truly a time when good news boosts one's spirits.
If it were him, he'd celebrate with a feast that lasts days and nights before saying anything else.
But the actual person is quite the contrary, always drinking alone in silence whenever he comes out.
In such a successful life, what is there to brood over?