Lots of RPGs have the kind of thing where you effectively power up in combat and get a bonus to a certain stat.
The "Create an Advantage" aspect in Fate Core seems to do something similar but not entirely the same. If in an exchange I wanted to say, "I stretch my legs and gain the limbered up aspect," I would have to make a roll, right?
My question: How do I set balanced Difficulties for something like that? Should it be the same every time? The rules say that Difficulty should depend on the scene, but actions like this don't seem to necessitate variance.
Edit: It seems weird, because for example, one of my characters has a stunt that says "Get +2 to Athletics to Create Advantages by sprinting to various distances throughout a zone." This character's Athletics is already +4, to a ---- would result in a total of +2 if the Stunt were used. Should it even be impossible to fail?