For many people the maintenance phase if often harder than the losing phase. Just as you hint at, during the losing phase you have a goal that you are woring toward. During maintenence you are just kind of hanging out - or so it seems.
I think you idea of shifting from a focus on the scale to a focus on fitnes is a great one! Toning can take all kinds of forms, running and other aerobic activities, resistance training and other weight lifting activities, or various dance-type classes, yoga, organized sports... the list is pretty long. The trick is to find one or 2 that you really enjoy and can stick with. It frequently takes a lot of testing, and most of us find that after a couple of years it is time to move on.
Many communities, churches, schools, and other organizations offer classes or clubs, so check into it, sign up or join, and find something that fits your lifestyle.
Good luck! in many ways the hard work is over, now it is time to reap the benefits of you new body.
2.5 years, 45 pounds later... 128ish pounds