I like the name of your thread, but you have to remember that in this world, there are no lucky charms, special incantations, or voodoo magic. Whether or not you succeed this time around is dependant completely on YOU. There are certain things that, at the age of 17, can be difficult to grasp. Though I am still only 23 myself, I look back at how I viewed the world at 17, and realize I had a lot to learn. still do really. and i was considered to be a very well experienced and adjusted young person, considering the various things life had thrown at me already, lol.
Take some time to sit down by yourself and just think. No TV, no books, no computer, no friends/family/pets, etc. Consider the things you place alot of value on in this world. and i dont mean monetary value. consider what types of things these are: material things, emotional feelings, or abstract ideas/philosophies? or any number of other things. then put those things into the context of a full lifetime, rather than just the last year or two of highschool or into college. what will have real lasting value over the next 70 years? understanding what things really mean to you will help you to achieve your goals and be the person you want to be. wanting things or doing something because someone else tells you to (read: family, friends, television, society, etc) will usually not provide enough motivation from within to succeed on the long term.
Hopefully at some point in thinking like this, you might have come across your health as something you value. If not, there is fortunately still plenty of time for you to learn the value of that. Though I certainly hope you learn it sooner rather than later. I know I wish I had learned it many years ago, and like I said, I am only 23 years old.
Once you realize what you value and why, you have to accept that for some things you will have to make changes to your lifestyle. and if you want to keep those things you value for a lifetime, you have to make those changes for a lifetime. All of this is directly important to the world of health, fitness, and weight loss. Even for someone who is not morbidly obese, or really even overweight, if you want to make improvements and prevent yourself from ever having these problems, you have to accept change.
I don't mean for all of this to scare you off, or seem like you need to have it all figured out at your age. You are young, and should enjoy your life at this stage, because things will change drastically in the next 5 years or so of your life. But, I hope I can at least inspire you to open up your mind, get out of the context of "here and now", and start thinking about what you care about and what you want to be in your life. There are some important things you will have to realize through this type of thinking if you ever want to achieve your own goals and desires, especially when it comes to health and fitness.
good luck to you, and I hope you are able to achieve what you want.