Red Mars by Kim Stanley Robinson

... the beige and yellow tiles they sat on had started to throb, as if lit from within; light gleamed on every water droplet covering the tiles, like tiny chips of lightning scattered everywhere, and Maya's body sprawled over the sparkling tiles pulsing before him like a pink candle. The intense thereness of it -- "haecceity," Sax had called it once, when John had asked him about his religious beliefs -- I believe in haecceity, Sax had said, in thisness, in here-and-nowness, in the particular individuality of every moment. That's why I want to know what is this? what is this? what is this? Now, remembering Sax's odd word and his odd religion, John finally understood him; because he was felling he thisness of the moment like a rock in his hand, and it felt as if his entire life had been lived only to get him to moment.

p. 265

And we only have this moment, for ever. Wow!