Boredom is nothing other than the sensation of the emptiness of existence. For if life, in the desire for which our essence and existence consists, possessed in itself a positive value and real content, there would be no such thing as boredom: mere existence would fulfil and satisfy us. As things are, we take no pleasure in existence except when we are striving after something – in which case distance and difficulties make our goal look as if it would satisfy us (an illusion which fades when we reach it) – or when engaged in purely intellectual activity, in which case we are really stepping out of life so as to regard it from outside, like spectators at a play. Even sensual pleasure itself consists in a continual striving and ceases as soon as its goal is reached.

- Arthur Schopenhauer, On The Vanity Of Existence