As a rule, I never attempt to set any type of structure for my short stories. It seems to make things more complex than they should be. It's far easier to just go right along with the flow and allow your mind to wander as your fingers write or type the words.
Setting a structure can of course be a good idea from time to time, especially if you plan on writing anything longer than the usual length of a short story, but it isn't necessary otherwise. Structure isn't all that helpful when it is constant.
Learn to adapt to flowing along with your words rather than planning ahead and knowing what you're going to say before you've even said it. There is no better way to grow bored with what you are writing, so try to avoid making this mistake when battling shorter tasks. It's only going to have you biting the desk when things don't quite work out as you've hoped they would.
Only set some form of structure if it is vital for your storyline.