The relation which connects the erotic content with the more general form of life as adventure is rooted in deeper ground. The adventure is the exclave of life, the "torn-off" whose beginning and end have no connection with the somehow unified stream of existence. And yet, as if hurdling this stream, it connects with the most recondite instincts and some ultimate intention of life as a whole - and this distinguishes it from the merely accidental episode, from that which only externally "happens" to us. Now, when a love affair is of short duration, it lives in precisely such a mixture of a merely tangential and yet central character. It may give our life only a momentary splendor, like the ray shed in an inside room by a light flitting by outside. Still, it satisfies a need, or is, in fact, only possible by virtue of a need which - whether it be considered as physical, psychic, or metaphysical - exists, as it were, timelessly in the foundation or center of our being. This need is related to the fleeting experience as our general longing for light is to that accidental and immediately disappearing brightness. 

Georg Simmel: The Adventure ("Das Abenteuer," Philosophische Kultur. Gesammelte Essays, [1911] 2nd ed.; Leipzig: Alfred Kroner (1919). Translated by David Kettler.)