I am addicted to junk food but I really need to diet?

I agree with your friend, what you should do is decrease your junk food intake , but dont completely cut it out of your diet... just start eating smaller amounts of it and yeah you can make it an occional ( once a week) thing if you can choose a special day for it and actually stick to that one day. but it may be more helpful to you to just eat a very small amount each day, since very small amounts will not affect you much.