You have to think positive instead of negative because otherwise your mind will be closed to change, and you won't allow happiness into your life again. There are always "what ifs" about the past. What if you had done this differently, or that, maybe your brother would still be alive. This is true. But what about the "what ifs" for the future? What if you preventing yourself from natural grieving and accepting happiness into your life, is actually blocking certain opportunities in the future? Chances you'll never get back. Chances to help others, to be a better person? There are so many unknowns in the future, and although most of our life is in the past, you got to look towards the future. Don't take this the wrong way, but you have to live your life to the fullest, for your brother. He doesn't have a future to live, so you have to do it for him, and for yourself, and live the best life you can.