You could write an essay on this one. Lots of meaning and symbolism. It’s about some old broken-hearted drifter, always was and still is, with nothing left but a memory. Wandering through life, lamenting he lost his dearest friend, not necessarily his lover but his only true love and it was his own fault. He’s got a place for his sleeping bag at her house in case he needs to take off. For whatever reason she’s left this life (rocks and ivy planted on their columns). He remembers when he broke her heart by leaving, too afraid or mixed up to tell her how much he really loves her. Maybe she took her own life because he left? He’s pretty much dropped out of the real world now. Too late to go back and undo the past, he lives in his own lonely grief, her memory is the only thing that makes him smile (tears of joy). Sad story but beautifully told in verse and music. Glen Campbell is underrated. His ability to play guitar was only surpassed by his songwriting.