We have no big "purpose" or mission, we only think we do because our brains are larger then other animals. However with modern society our lives have more meaning (even though as an individual we are less signifigant then ever before) then at any other point in time... You could say that for materialistic people which is pretty much all of us, if you compare our civilization to other's in history, our sole motivation is to succeed as an individual so we can have everything we desire and to breed to pass on our life's work. Modern civilisation is the only time in history that any species is able to fufill all their want's and desires and still crave more.