We are an imperfect product of evolution in an imperfect universe which came into being without any purpose. All the things material, from a simple unicellular organism to a very complex cellular human body, are made up of certain ingredients in some proportions environmentally determined, but far from being perfect either in composition or function.
All living and non-living bodies have to undergo routine wear and tear and withstand the vagaries of Nature. We fight to survive and this continues till the failure of this imperfect body. We die but not without inflicting some changes on the very environment which was responsible for our rise and eventual demise.
The genes we pass on to posterity make it better equipped to fight the environment on those exposed fronts. But the imperfections on both sides (Nature as well as individual) open new battle frontiers for us in the fight for survival. And the show goes on.