Seneca, Epistulae ad Lucilium 1.7:
“You ask me what I think chiefly to be avoided? A crowd. You cannot yet be safely entrusted to it. I will certainly confess my own weakness: I never bring back the habits which I took with me. Something which I previously ordered is disturbed, something which I previously banished simply returns. As it happens with the sick, whom a long illness has affected to such a degree that they can no longer go out without harm, so it happens with us whose minds are recovering from a long disease. Association with many people is a hateful thing: in the crowd, there is no one who will not commend his vice to us, or even impress and smear it upon us without our knowing. In every case, the greater the crowd with whom we mingle, the greater the danger. But nothing is so dangerous to good morals as to loiter around at a show, where our vices steal upon us all the more readily on account of their pleasure. What do you think I am saying? That I come back more avaricious, ambitious, and prone to luxury? Nay, rather, I return more cruel and inhumane because I have been among humans.”
Quid tibi vitandum praecipue existimes quaeris? turbam. Nondum illi tuto committeris. Ego certe confitebor imbecillitatem meam: numquam mores quos extuli refero; aliquid ex eo quod composui turbatur, aliquid ex iis quae fugavi redit. Quod aegris evenit quos longa imbecillitas usque eo affecit ut nusquam sine offensa proferantur, hoc accidit nobis quorum animi ex longo morbo reficiuntur.  Inimica est multorum conversatio: nemo non aliquod nobis vitium aut commendat aut imprimit aut nescientibus allinit. Utique quo maior est populus cui miscemur, hoc periculi plus est. Nihil vero tam damnosum bonis moribus quam in aliquo spectaculo desidere; tunc enim per voluptatem facilius vitia subrepunt.  Quid me existimas dicere? avarior redeo, ambitiosior, luxuriosior? immo vero crudelior et inhumanior, quia inter homines fui.