This is from The Thief of Time by Terry Pratchett. I haven’t read any Pratchett but maybe I need to start this this one:
The universe is, instant by instant, recreated anew.
Therefore there is in truth no past, only a memory of the past. Blink your eyes, and the world you see next did not exist when you closed them.
Therefore, the only appropriate state of the mind is surprise.
The only appropriate state of the heart is joy.
The sky you see now, you have never seen before.
The perfect moment is now.
Be glad of it.