I will leave it for the present, as this letter is already pretty long. Such is my desire, my anxiety for your perfection, that I never think I have said enough, though you may possibly think I have said too much; and though, in truth, if your own good sense is not sufficient to direct you, in many of these plain points, all that I or anybody else can say will be insufficient.

Lord Chesterfield (1694-1773) English statesman, wit [Philip Dormer Stanhope]

Letter to his son, #168 (18 Nov 1748)
    (Source)

Chesterfield repeats the sentiment in a later letter, #194 (22 Sep 1749):

This letter is a very long, and so possibly a very tedious one; but my anxiety for your perfection is so great, and particularly at this critical and decisive period of your life, that I am only afraid of omitting, but never of repeating or dwelling too long upon anything that I think may be of the least use to you.