The best always come at a burst, spontaneously and as it were inspirationally.

A laboured sonnet is a dull piece of artificial rhyming, and as it springs not from the heart of the writer, fails to reach the heart of the reader.

If the metal does not flow out quick and hot, there never can be a sharp casting.

Good sonnets are crystals of the heart and mind, perfect from beginning to end, and are only unpopular where poetasters make a carnal toil of them instead of finding them a spiritual pleasure.

But one who knows his theme may write reams about sonneteering; for instance, see that striking article on Shakespeare's sonnets in a recent _Fortnightly_ (or was it a _Contemporary_ ?) by Charles Mackay, himself one of our literary worthiest, who has so well worked through a long life for his country and his kind: my best regards to him.
His discovery, or rather ingenious hypothesis, quite new to me, is, that some of the one hundred and fifty-four in that collection are by other writers than Shakespeare, though falsely printed under his name, and that some more (though by him) were written impersonately in the characters of Essex and Elizabeth; which would account for an awkward confusion of the sexes hitherto inexplicable.