Artists needed to develop thick skin in order to survive in their line of work.
They earned their livelihoods by presenting their works to the public.
A crowd contained all kinds of random people and personalities. Each of them could supply very different feedback from uncritical praise to a torrent of horrible insults.
Of course, the Impresario Prince's identity vastly limited the amount of flaming he received, but he must otherwise suffer the same tribulations as any other artist.
Given the fact that the man had stuck by his career for so long, Prince Casevir must have been able to develop his own way of coping with harsh criticism. Such an artist should no longer be easily swayed by any feedback, no matter whether it was positive or negative.