In the world in which time is a circle, every hand shake, every kiss, every birth, every word, will be repeated precisely. So too every moment that two friends stop becoming friends, every time that a family is broken because of money, every vicious remark in an argument between spouses, every opportunity denied because of a superior's jealousy, every promise not kept.
And just as all things will be repeated in the future, all things now happening happened a million times before. Some few people in every town, in their dreams, are vaguely aware that all has occurred in the past. These are the people with unhappy lives, and they sense that their misjudgements and wrong deeds and bad luck have all taken place in the previous loop of time. In the dead of night, these cursed citizens wrestle with their bedsheets, unable to rest, stricken with the knowledge that they can not change a single action, a single gesture. Their mistakes will be repeated precisely in this life as in the life before. And it is these double unfortunates who give the only sign that time is a circle. For in each town, late at night, the vacant streets and balconies fill up with their moans.
- Eistein's Dreams, a novel by Alan Lightman