In either case the orator should bear clearly in mind throughout his whole speech what the fiction is to which he has committed himself, since we are… - Quintilian

For it is an ordinance of nature that nothing great can be achieved in a moment, and that all the fairest tasks are attended with difficulty, while on births as well she has imposed this law, that the larger the animal, the longer should be the period of gestation.

We should not speak so that it is possible for the audience to understand us, but so that it is impossible for them to misunderstand us.

Neque enim tantum id dico, eum qui sit orator virum bonum esse oportere, sed ne futurum quidem oratorem nisi virum bonum. Nam certe neque intellegentiam concesseris iis qui proposita honestorum ac turpium via peiorem sequi malent, neque prudentiam, cum in gravissimas frequenter legum, semper vero malae conscientiae poenas a semet ipsis inproviso rerum exitu induantur.