From the eponymous 1967 album by The Merry-Go-Round, it's Emmit's often covered and truly exquisite "Time Will Show the Wiser."

A great track, obviously, but the thing about it that really hits me over the head of late is -- what a young man's song it is, at least lyrically. I mean, we all know the feeling, but I can't imagine many people past their teens who'd be capable of articulating it so nakedly and naively.
Of course, the Beatles/psychedelic touches are pretty damned sophisticated for a bunch of guys barely out of a high school when they recorded it.