This isn't really an aesthetics question, but a question of interpreting a poem philosophically; a kind of philosophical hermeneutics of poetry; Rilke is well-known as a metaphysical poet.
Towards the end of the first stanza of the first Elegy of the Duino Elegies Rilke writes:
Have you remembered
Gastara Stampa sufficiently yet, that any girl,
whose lover has gone, might feel from that
intenser example of love: ‘Could I only become like her?’
Should not these ancient sufferings be finally
fruitful for us? Isn’t it time that, loving,
we freed ourselves from the beloved, and, trembling, endured
as the arrow endures the bow, so as to be, in its flight,
something more than itself? For staying is nowhere.
He invokes the unrequited passion of Gastara Stampa for the young Lord of Treviso, inverting the protagonists of the traditional Islamic tale of Majnun & Layla; this tale of romance is often invoked in Islamic mysticism for the unrequited desire to lose oneself in the Infinite.
He asks have we remembered her - that is remembered her passion; but is this 'sufficient' remembrance when we do not remember her dying? He asks should you 'become like her' - in her living or in her dying.
Rilke, asks "should not these ancient sufferings be finally fruitful for us"; ancient as they date from the discovery of the Infinite by the nomads of grassy steppes of the Eurasian landmass under the infinite sky; suffering and unfruitful as unrequited.
He asks should we not turn away and 'free ourselves' from the love of the impossible, the unattainable beloved (the beloved being the symbol of Allah in sufi poetry) to that of the possible; not agape but eros; and being eros - fruitful.
Thus to be thrown upon (as Heidegger later would put it) and 'endure' the world as arrow endures the bow; and by living authentically - that is in our flight, our trajectory of living - we become something more than what we were when we were 'trembling' in the knowledge of our impermenance ('staying is nowhere')
Trembling of course is one half of the title of Kierkegaards philosophical book Fear and Trembling - his meditation on the Abrahams covenant. He is considered as the main precursor to European Existentialism.
Is this sufficient evidence to claim, at least in this stanza, that Rilke invokes Existentialism as a solution to the problems of living (or loving)?