Sir James

During a rehearsal of one of his plays, Sir James M. Barrie became increasingly irritated with the producer's young son, who was convinced that he knew it  all.

Repeatedly, the youth interrupted the rehearsal to criticize one of the principals.

After one such outburst, Barrie turned to him and said, "My boy, you will have to be more patient with us. After all, we are not young enough to know everything."