Why am i letting myself fail?

It seems as you have no self-confidence, "I have an incredibly short attention spam." which means your life is going to suck. This is your first and most destructive quality. Think of your body like this... It is a chemical experiment and anytime you put something into it it changes the chemistry. So you eating a non balance diet uming since you almost died from energy drinks. I suggest you control yourself on what you eat and practice disciple. When the brain is communicating ,like remembering a thing on the exam, you have to be on the same chemicals in your body for maximum success of remembering. You need to get your schedule down where you are secure with your proper study time and work. You don't always need to go out and party and your friends should respect that with your current situation of almost dieing. Your note I think should never have been written. Or get ADD and get yourself some Aderal to concentrate.