Long hairstyles are really not recommended for long, narrow faces. The longer the hair, the longer the face will look. This is because when your eyes look at the face, they incorporate the hair as part of it. So if you have hair down to the middle of your back and you're wearing it in the front, it makes your face seem even more longer than it is.
However, if you can't part with your long hair, you can add major layers to compensate for the length. This will not only help to take some weight off of the style to boost fullness but will also give the illusion that you have a shorter face because of the major-body style you'll be sporting. Adding bangs is a definite plus because it will create the illusion that you have a shorter face. Try doing some blunt bangs to see a major difference. Blunt bangs that hang almost parallel with the eyebrow are really in right now.