From the beginning I was focused on the end. I hardly remember the bliss of not pondering our finite existence. I think many of us progress to asking questions but we fear too greatly what the answers may be, so we pull the covers back over our head. The world is full of many safety nets to the questions that scare us, and many of us are apt to cling to those reassurances. I believe that despite the trouble, it is worth it to live on the edge with no harness, net, or bubbles to ease your mind.
Why? Why are we here? I've stopped looking for a purpose because this world is a purposeless place. I can answer your question of why, and the answer is nothing. You have no innate purpose. If you are clever, you will realize this is not depressing but rather a freeing realization. If you have no purpose you are able to create your own. You choose your own destiny, and only you can judge if you have fulfilled it or not.
This life is a game, and there are many ways to play. The rules are very simple: find joy for yourself, and bring joy to others. Everyone simply wants to look back before they leave and say: "I made the most of my time. It was worth it." I often ask myself if living is truly worth it. We're destined to die sometime, what difference would it make when? I'm afraid the best answer I've found is in how it would affect others. Those closest to me do not deserve the grief a loss would bring them.
Why must death be sad? We have a bad habit of clinging on to what is good, and pushing away what is bad. I no longer believe life is good and death is bad. Everything is just, everything. Life would not be so amazing in the soothing sunshine if you did not also experience the chilling rain. Life is about balance. Death is a necessary component to making us appreciate the time we do have, and thus we should love it. One day you, I, and everyone else will fade away. All I ask is that you no longer fear this universal truth. I ask that you embrace it with all your heart, and welcome it when the time comes. Until we talk again, goodbye.