My book club read The Measure, by Nikki Erlick, where one day all adults received a string in a box, with the length of the string perfectly correlating with their total lifespan, and children received them too, as they grew into adults. The box and string were indestructible.

Several members of the book club were going through a memento mori existential crisis, and all I cared about was that no one had done anything interesting with the indestructible materials. Imagine what humanity could accomplish with billions of indestructible boxes and strings.

Ah, lol. Before you edited it I thought you meant you were going to see yourself commit suicide. (I assumed you were the one operating the time machine)