Meaning of “A boy’s love comes from a full heart;…”

The Idle Thoughts of an Idle Fellow, “On Being in Love”; the comparison opens the essay’s mock-medical treatment of romance.

An Essay on Criticism, Part III; Pope joins good nature and good sense before contrasting ordinary human error with the higher moral act of forgiveness.

Indian Summer of a Forsyte, represented in Project Gutenberg #2594. Irene says the line to old Jolyon while speaking about her dead lover; it is emotionally charged fictional dialogue, and the surrounding conversation immediately gives old Jolyon a more ironic response.

Howards End, Chapter XXII, Project Gutenberg #2946. The narrator summarizes Margaret’s hope of reconciling “the prose and the passion” in Henry with “Only connect! That was the whole of her sermon.” The sentence belongs to the novel’s thematic and character context rather than serving as a complete formula for every relationship.

Three Men in a Boat, packing episode; the narrator describes Montmorency repeatedly inserting himself into whatever the men are trying to pack.

Barchester Towers, Chapter XXVII, ‘A Love Scene,’ Project Gutenberg #2432. Madeline Stanhope tells Mr Slope that there is no happiness in love except at the end of an English novel after a comic catalogue of tragic lovers. The sentence is witty fictional dialogue inside Trollope's satire, not a factual rule about love or happiness.