Yes! they wander on In gladness all; but thou, methinks, most glad, My gentle-hearted Charles! (27-29)
Coleridge repeats the phrase "wander on in gladness" several times throughout the poem. His friends have a fine appreciation for nature, but the speaker feels a special fondness for Charles Lamb, who has been deprived of nature and happiness because of circumstances in his life. Maybe Coleridge admired the way Lamb dealt with his setbacks because Coleridge had (or was to have) so many setbacks of his own (opium addiction, a failed marriage, the list goes on and on).
For thou hast pined And hunger'd after Nature, many a year, In the great City pent, winning thy way With sad yet patient soul, through evil and pain And strange calamity! (29-33)
Charles's soul is fundamentally "sad" or melancholy because of what he has been through – the death of his mother at his sister's hands, among other things. But Charles suffers through hardship with "patience," knowing that better days lie ahead.
So my friend, Struck with deep joy, may stand, as I have stood, Silent with swimming sense; yea, gazing round On the wide landscape (38-41)
The speaker knows that Charles is capable of having a deeply spiritual experience like the ones he has had. Is his admiration for Charles a form of self-admiration?
My gentle-hearted Charles! when the last rook Beat its straight path along the dusky air Homewards, I blessed it! deeming its black wing (Now a dim speck, now vanishing in light) Had cross'd the mighty Orb's dilated glory While thou stood'st gazing (69-74)
After his epiphany at the beginning of the third stanza, he overflows with feelings of good will and brotherly love. His statement about blessing the rook has the tone of, "Guess what I did? Tee-hee." Or maybe we just like the idea of Coleridge giggling like a schoolgirl.
and had a charm For thee, my gentle-hearted Charles, to whom No sound is dissonant which tells of Life. (75-77)
The end of the poem reveals what might be Charles's most admirable character trait: his ability to integrate unpleasantness and suffering into the harmony of a full life. The end might also hint at the need to harmonize an individual life with the greater unity of Nature – a classic Romantic idea.