Seneca · On the blush of modesty
Letters 11.10
Choose therefore a Cato; or, if Cato seems too severe a model, choose some Laelius, a gentler spirit. Choose a master whose life, conversation, and soul-expressing face have satisfied you; picture him always to yourself as your protector or your pattern. For we must indeed have someone according to whom we may regulate our characters; you can never straighten that which is crooked unless you use a ruler. Farewell.
Seneca, Letters to Lucilius 11.10, translated by Richard Mott Gummere