The phrase Richard’s himself again is used to indicate that a person has returned to normal after an illness or similar episode.

This phrase originated in the following dialogue between Catesby and Richard, from The Tragical History of King Richard III. As it is Acted at the Theatre Royal (London: Printed for B. Lintott and A. Bettesworth, [1700]), an adaptation of Shakespeare’s Richard III by the English actor, author and theatre manager Colley Cibber (1671-1757)—Context: The night before the Battle of Bosworth Field, Richard was visited by the ghosts of his victims:

Enter Catesby.
Cat. ’Tis I, my Lord; the Village Cock
Has thrice done salutation to the morn:
Your friends are up, and buckle on their Armour.
Rich. ‘O Catesby! I have had such horrid dreams.
Cat. ‘Shadows, my Lord, below the Soldier’s heeding.
Rich. Now, by my this days hopes, shadows to night
‘Have struck more terror to the Soul of Richard,
Than can the substance of ten Thousand Soldiers
Arm’d all in Proof, and led by shallow Richmond.
Cat. ‘Be more your self, my Lord: Consider, Sir;
‘Were it but known a dream had frighted you,
‘How wou’d your animated Foes presume on’t.
Rich. Perish that thought: No, never be it said,
That Fate it self could awe the Soul of Richard.
Hence, Babling dreams, you threaten here in vain:
Conscience avant; Richard’s himself again.
Hark! the shrill Trumpet sounds, to Horse: Away!
My Soul’s in Arms, and eager for the Fray.      [Exeunt.

The corresponding passage is as follows in The Tragedy of King Richard the third (London: Printed by Valentine Sims, for Andrew Wise, 1597), by the English poet and playwright William Shakespeare (1564-1616):

Enter Ratcliffe.
Rat. My Lord.
King. Zoundes, who is there?
Rat. Ratcliffe, my Lord, tis I, the earlie village cocke,
Hath twise done salutation to the morne,
Your friendes are vp, and buckle on their armor.
King. O Ratcliffe, I haue dreamd a fearefull dreame,
What thinkst thou, will our friendes proue all true?
Rat. No doubt my Lord.
King. O Ratcliffe, I feare, I feare.
Rat. Nay good my Lord, be not afraid of shadowes.
King By the Apostle Paul, shadowes to night,
Haue stroke more terror to the soule of Richard,
Then can the substance of ten thousand souldiers,
Armed in proofe, and led by shallow Richmond.
Tis not yet neere day, come, go with me,
Vnder our tents Ile plaie the ease dropper,
To see if any meane to shrinke from me.       Exeunt.

The earliest recorded use of the phrase occurs, with explicit allusion to Colley Cibber’s play, in the following letter, published in A series of genuine letters between Henry and Frances (London: Printed for W. Johnston, 1757), by Richard Griffith (d. 1788) and Elizabeth Griffith (1720?-1793):

Musaeum.— Chere Mignonne,
I am heartily fatigued with our Assizes, where we had a great deal of Hanging, Wrangling, and Duelling, with other Amusements of that Kind; which, however, was some Relief to me, after our Parting, as the Company of Fools, or Knaves, must, for the Time, quite exclude any Thought of you from my Mind, and give me less Leisure to lament your Absence. But I am now returned to myself, and, by giving up myself intirely to you, may say with Glocester *,
Richard’s himself again.

* Richard (1452-1485), Duke of Gloucester, was crowned as King Richard III in 1483.

The earliest occurrence of the phrase that I have found is from The Observer (London, England) of Sunday 21^st December 1800:

The Sequel.

In a former Number we mentioned a novel adventure in Mary-le-bone, and the very embarrassed predicament in which a young lady was placed by the angry impetuosity of a Scotch Baronet, to whom her faith had been plighted, opposing her more prudent nuptials with a rich provincial Knight.—The affair it was thought would have afforded amusement to the Court of King’s Bench, but we are disappointed by both of the lovers flying the field of battle, and throwing up their claims.
It will be remembered, that as the lady entered the carriage to join her ancient Lothario at the altar, the young Baronet followed her, and, by the production of pistols, compelled her to swear she would not marry his rival.—Whether his passion evaporated in this ebulition [sic], or that he thought the woman who could sacrifice her word and her affection to mercenary considerations not calculated to promote his happiness, we will not pretend to say; but with somewhat more of prudence than of gallantry, “he gave his love to the wind,” and with fair occasion renounced his pretensions.
Sir Alderman […] got, our readers will recollect, as far as the altar, which, some how or other, oftentimes has a marvellous effect in generating repentance amongst its antique votaries […].
[…] The Knight’s time was not yet come. Reflection, which spoils many a pretty match, […] in a short time so completely got the better of his love, that on going to her house, he, with all the coldness of an anchorite, heard her repeat the vows his rival had imposed on her.—In fine, he submitted to his fate with stoic philosophy, and setting off for H——, resolved to pass the remainder of his days in the quiet, though dull and unprofitable state of celibacy.
[…] She followed the Knight into the country, and reached his house at midnight.—Arousing him, she essayed “all the Nature, all the Art of Love;” but to no effect.—“Richard’s himself again!”—and having refreshed her with ham and chicken, sent her back disconsolate to town.