I think it was Kierkegaard who said that while life is lived forwards, it can only be understood backwards. Certainly most art proves the truth of this statement. While life presses on breathlessly and leaves nary a moment for sense-making, artists are the ones who press pause and rewind, arranging the pieces, plot-points and colors for us in such a way that the full (or fuller) picture is seen.
A professor I admire once said — while discussing the films of Yasujiro Ozu, or maybe it was semiotics (can’t remember) — that watching the sun set can be both a thing of incredible beauty and deep sadness, often simultaneously. I thought of this as I watched Richard Linklater’s Before Midnight, which includes a scene of a couple sitting by the sea in Greece, watching the sun slowly dip below the horizon. It’s there, there, there — and then it’s not there. A fleeting flare of arresting orange. Present and then absent. Perhaps the beauty and sadness of a sunset has to do with the fact that it’s the process in nature we humans most identify with. Ours is a context of ephemerality.
Part of the sadness and elegiac quality of something like commencement is that we remember what it was like to be young and free, "Golden in the mercy of his means," with the world as our oyster. We lament that we've lost the sense of adventure, bravery, and risk that electrified those long lost days. And yet the truth is we need not abandon such things. We should be lifelong learners, career explorers, always re-imagining the world and discovering its wonders anew.