If, for example, you were trying to do Blitzen mission but were sitting on a high level not wanting to continue, you can ride the Magic Carpet. It will ask you do complete missions. If it asks you to complete a level of Blitzen you can cancel the Magic Carpet without starting/failing Blitzen and then wait to do Magic Carpet again and hope it doesn't ask for a Blitzen mission, but you can keep redoing the Magic Carpet until you can get through it without being asked for Blitzen.
