Curse.
Unless you can stop cold the effects of aging, your body will still fall apart – albeit more slowly. Sounds torturous.
Also, at some point, everyone you ever knew will be dead, leaving you alone with fading memories and fewer options for companionship.
Lastly, unless this were a planet-wide phenomenon, you would eventually be hounded relentlessly by the media and by scientists and doctors as a freak. So you’d eventually have to live as a hermit.
All in all, sounds pretty miserable.