I could easily see it going two ways. It goes away as soon as you force what ever it is back to the Nevernever, draw a circle around yourself to cut the magic tie or what ever else you can thing of for that. Alternatively though, I think you could easily explain that not working with some kind of "feeding off your energy" type of explanation and make an antidote the solution. Depends on what you're going for, I suppose. Definitely could go ether ways.