Hi HazerFazer
I wish I had an answer for you that would fix your problem today. I wish it were that easy.
First, one thing that might be compounding your difficulties at this time is simply your age. I found 16 to be difficult. My emotions had so many peaks and valleys. Some of this I suspect was simply hormones; some was likely poor nutrition; and some I think was that I simply did not have the perspective of experience by which to engage the events in my life.
Second, it is so easy to set oneself up for failure, which becomes a self-fulfilling prophecy. For example, since it is that time of year where people will be thinking of New Year's resolutions. So one decides to commit to a healthier diet and exercise program. After 3 or 4 days of "success" the reality that such a big lifestyle change is hard. So after a comfort cookie or three, the decision is made that since one has now "failed" one might as well give up altogether. So my advice is: make it easier for you to succeed. Often. Since fitness is important to you, focus on hitting your workouts at least 90% each week or month. Keep a log of your progress. Some days you will be fatigued from the last workout and will not be as strong. That is OK and normal. The important thing is to stick with it.
One blog that I have found helpful recently is
Colm OReilly . He has a series of articles on confidence and self-acceptance which might be helpful to you.
Finally, it is easy to get caught in the snowball of despair. If this --> then that ---> then this worse thing, etc. It just gets bigger and worse with each iteration. Pondering all of these bad outcomes will not bring joy and hope into your life. I have a tendency to do this and have finally taught myself to stop. I cannot express how much happier I have been since I have. Long story: About 5 years ago I was on a business trip out of state and could not reach my husband by phone. I worked myself into a terrible state. I was convinced that he must have gone out, got drunk, drove off the road and was in the hospital or dead; our cats must be starving, etc. I rushed to the airport in the middle of the night to rush home. The logical part of my brain knew this was ridiculous and yet there I was racing home with only the very worst thoughts in my brain. My husband had, it turned out, gone to a friends house and fell asleep on the couch.
This event taught me some very important lessons. One, I wasted a lot of time and energy creating many bad possible futures. Two, even if I was correct, rushing home would have changed nothing. So for the most part, if things are out of my control, I tend to choose to think that the outcome will be positive. Yes, the outcome may yet be bad but I will muddle through if the bad stuff comes to pass. I firmly believe that hope and joy are a choice. Choose joy.