Wow. A deep question. I'm sorry, but there are no easy or simple answers. The truth is that life is not fair. There will always be suffering in life. We have to be strong. Personally, I found some answers from studying Buddhism. The Buddha said that life contains dukkha, (or suffering,) but that this is not really what makes us unhappy. Instead, we are unhappy because we want life to be fair and free from pain. But this is not real life. Everyone gets sick, gets old and will die. You can either accept it or try to fight against it. (For example, if you want to be young forever, then you will be very unhappy when you finally become older.) This idea is similar to something called the "Serenity Prayer". It states, "May God give me the courage to change the things I can, the serenity to accept the things I cannot change, and the wisdom to know the difference." That's the best advice I can offer you. Hope it helps. BTW, (this means "by the way,") I notice you are Korean. So I am curious. Were you thinking of the people in North Korea when you asked this question?