A delight Comes sudden on my heart, and I am glad As I myself were there! Nor in this bower, This little lime-tree bower, have I not mark'd Much that has sooth'd me. (45-49)
He has an epiphany at the beginning of the third stanza: he's not alone after all! The feeling of isolation melts away thanks to the work of his imagination.
Henceforth I shall know That nature ne'er deserts the wise and pure; (60-61)
Coleridge is no longer isolated, but does he feel connected to his friends, or only with nature? From these lines it seems that nature is a suitable substitute for Lamb and the others. Or maybe he feels comfort in fact that he can share in Lamb's joy, even at a distance.