Pectus est enim quod disertos facit, et vis mentis. - Quintilian

Qui stultis videri eruditi volunt stulti eruditis videntur.

I do not merely assert that the ideal orator should be a good man, but I affirm that no man can be an orator unless he is a good man. For it is impossible to regard those men as gifted with intelligence who on being offered the choice between the two paths of virtue and of vice choose the latter, nor can we allow them prudence, when by the unforeseen issue of their own actions they render themselves liable not merely to the heaviest penalties of the laws, but to the inevitable torment of an evil conscience.

So much easier is it to do many things than to do one thing for a long time continuously.