Technological/Cognitive Weirdtopia: Everyone runs on computronium, in a simulation that starts out rather like normal, but everybody has an undo button: at your option you can undo everything except progress made in your own mind, up to any point in your life since the simulation began. There are safeguards in place to prevent two people from doing this at the exact same time, but otherwise there are no limitations on use; you can redo a second or a century, once or a thousand times. It takes a lot of "real" time for the simulation to progress to everyone's satisfaction beyond the first five minutes.