The speaker starts with a bleak image: the heart as a grave or a prison, a place where feeling is either buried or locked up. Then comes a question that nobody can really answer: who could remember what it was like to be let out? The question suggests that being closed off has gone on so long that freedom feels almost forgotten, maybe even unimaginable.
The last two lines shift to something small and practical. The speaker takes "a bottle or two" and goes "hunting for friends." It's a casual, slightly wry way to describe a search for company, and the drink hints at a need for help in loosening up. The word "hunting" makes the search feel a little desperate, as if connection has to be tracked down rather than simply enjoyed.
The mood is lonely but not melodramatic. The poem moves from heavy imagery to a plain, almost offhand action, and that contrast makes the speaker's isolation feel real and quietly sad, with a faint thread of hope.