Source, in full
English proverb, used by many authors, including some prior to Margaret Fuller's time; Thomas Fuller expresses related thoughts in his "Panegyric" on Charles II, Section 21" in The History of the Worthies of England (1662)
Notes from Wikiquote
Be you above your ancestors renown'd,
Whose goodness wisely doth your greatness bound;
And, knowing that you may be what you would,
Are pleased to be only what you should.