How to gracefully step down from an interim position?

My boss resigned last year and I was asked to serve as his replacement on an interim basis. It has now been determined and agreed by myself and upper management that I will not continue in this role since there have been many recent changes in the company. How do I save face? I have been told that I will be considered for the management position again, after I gain a little more experience. I will be returning to my last position with some additional responsibilities.