When you propagate a cactus, you twist a piece off. You allow the cut end to callus over. How long depends on the size of the cactus. It could be two weeks. It could be eight weeks. It’s as long as it takes for the cactus to form a callus over the place where it was once rooted to something else. Only then is it ready to be replanted as its own.
When something you were working on withers to the ground, either from never being finished, or just being bad (I often make things that are both at the same time), you could just let it gather dust and decompose. You could also go find the one line of dialogue that captured why you wanted to create in the first place, and twist the piece off. You do nothing with it next. Allow the end to callus over. Allow what once carried you away to end where this now begins. It must learn to not be rooted to anything but itself.
There is work I am planning to revisit. The kind where so many rewrites and reworking of the plot just never produced what I set out to do. I will line up all the twisted off pieces under the sun and allow the cut ends to callus over. Eventually, once replanted, one might even find new roots.