Letters 122.17

You should not be surprised at finding so many special manifestations of the vices; for vices vary, and there are countless phases of them, nor can all their various kinds be classified. The method of maintaining righteousness is simple; the method of maintaining wickedness is complicated, and has infinite opportunity to swerve. And the same holds true of character; if you follow nature, character is easy to manage, free, and with very slight shades of difference; but the sort of person I have mentioned possesses badly warped character, out of harmony with all things, including himself.

Seneca, Letters to Lucilius 122.17, translated by Richard Mott Gummere