Love is like the wild rose-briar,
Friendship is like the holly-tree—
The holly is dark when the rose-briar blooms
But which will bloom most constantly?
The wild rose-briar is sweet in spring,
Its summer blossoms scent the air;
yet wait till winter comes again
And who will call the wild-briar fair?
What clues do these supporting details provide about the poem’s main idea?