Quintilian Institutio Oratoria 1.2.18

[18] It is above all things necessary that our future orator, who will have to live in the utmost publicity and in the broad daylight of public life, should become accustomed from his childhood to move in society without fear and habituated to a life far removed from that of the pale student, the solitary and recluse. His mind requires constant stimulus and excitement, whereas retirement such as has just been mentioned induces languor and the mind becomes mildewed like things that are left in the dark, or else flies to the opposite extreme and becomes puffed up with empty conceit; for he who has no standard of comparison by which to judge his own powers will necessarily rate them too high.