OMG HELP ME!!!!

WHAT DO YOU DO IF YOU MISS SOMEONE SO BADLY AND THEY DON'T GO TO YOUR SCHOOL ANYMORE AND DOESN'T VISIT ANYMORE? HOW DO YOU HANDLE THAT? I MEAN KNOWING THAT I STILL HAVE DEEP FEELINGS FOR THAT PERSON BUT CAN'T DO NOTHING ABOUT IT. I FEEL LIKE WHEN THAT PERSON IS NOT THERE I HAVE NO ONE. LIKE IF MY WORLD WAS OVER. I CAN'T THINK STRAIGHT. IT'S LIKE HALF MY BRAIN DIED AND WENT AWAY WITH THEM. AND THEN MY HEART HAS STOPPED POUNDING AND NOW I FEEL LIKE I'M DEAD. THAT NONE OF ME EXIST ANYMORE. IT'S OVER FOR ME.