Mistakes or errors happen often when printing. How you recover from them is just as important. Sometimes you can let it just keep on going and get a partial success, especially when you are making many duplicates of something. For my new printer I am trying to make it out of mostly printed parts. This includes the beams that make up the shape of the printer.
Often tall slender objects will fail because they lose contact with the build plate. The leverage the nozzle has against the holding surface only increases as the parts grow taller. In this picture one of the beams had come loose from the surface about halfway through. It took it 6 hours to get this far, with another 3 to go. In this case it was better to just let it finish, having 5 successful beams instead of 6.