It is what gives life meaning. There is no answer to "why" things happen... Unless you're religious, then there is an answer. Things good, bad and neutral just happen. It doesn't matter your age or how much you pray and go to church... Bad things and good things happen.
Would you still appreciate the presence of family and friends if no one ever died? Would you be able to distinguish between the good times when you've never experienced bad ones? What kind of life would it really be if everything that happened was good and no one ever experienced loss? From where you stand it probably sounds great, but that's only because you've experienced the opposite.
The only way to get through is to come to terms with this. You have to recognize that peaks and valleys happen through life, and the more you keep moving forward the better chance you'll have of moving back to a peak. If you struggle with this, it may be wise to talk to someone and learn some coping skills... We all tend to cope differently.