Sri Aurobindo
Letters of Sri Aurobindo
Volume IV - Part 2
It is the ordinary nature of vital love not to last or, if it tries to last, not to satisfy, because it is a passion which Nature has thrown in in order to serve a temporary purpose; it is good enough therefore for a temporary purpose and its normal tendency is to wane when it has sufficiently served Nature’s purpose. In mankind, as man is a more complex being, she calls in the aid of imagination 
and idealism to help her push, gives a sense of ardour, of beauty and fire and glory, but all that wanes after a time. It cannot last, because it is all a borrowed light and power, borrowed in the sense of being a reflection caught from something beyond and not native to the reflecting vital medium which imagination uses for the purpose. Moreover nothing lasts in the mind and vital, all is in a flux there. The one thing that endures is the soul, the spirit. Therefore love can last or satisfy only if it bases itself on the soul and spirit, if it has its roots there. But that means living no longer in the vital but in the soul and spirit.
The difficulty of the vital giving up is because the vital is not governed by reason or knowledge, but by instinct and impulse and the desire of pleasure. It draws back because it is disappointed, because it realises that the disappointment will always repeat itself, but it does not realise that the whole thing is in itself a glamour or, if it does, it repines that it should be so. Where the vairagya is sattwic, born not of disappointment but of the sense of greater and truer things to be attained, this difficulty does not arise. However the vital can learn by experience, can learn so much as to turn away from its regret of the beauty of the will-o’-the-wisp. Its vairagya can become sattwic and decisive.