The canker-worm of every gentle breast. [ Spenser ]

Loathsome canker lives in sweetest bud. [ Shakespeare ]

In the sweetest bud
The eating canker dwells; so eating love
Inhabits in the finest wits of all. [ William Shakespeare, Two Gentlemen of Verona,  Act I. Sc.1 ]

Banish the canker of ambitious thoughts. [ William Shakespeare, Henry VI ]

Yet is there one more cursed than they all.
That canker-worm, that monster, jealousie,
Which eats the heart and feeds upon the gall,
Turning all love's delight to misery.
Through fear of losing his felicity. [ Spenser ]

My days are in the yellow leaf;
The flowers and fruits of love are gone;
The worm, the canker, and the grief, Are mine alone. [ Byron ]

That eating canker grief, with wasteful spite, preys on the rosy bloom of youth and beauty. [ Rowe ]

Misery is caused for the most part, not by a heavy crash of disaster, but by the corrosion of less visible evils, which canker enjoyment and undermine security. [ Dr. Johnson ]