There is absolutely no reason and certainly no evidence to support the notion of a divinely gifted "purpose", some holy mission that all living things share.
It is true that all living organisms will share some common, basic traits; The instinct toward individual survival, and procreation. For humans, who have adapted and evolved in such a way that we are - uniquely amongst living species- capable of abstract thought, capable of framing a debate about whether the divine exists or not, or whether life has a purpose, that purpose for each individual comes from the individual themselves.
For one person their purpose in life might be defined by having a family; For another it might be about playing sport, for someone else it might be to explore the unknown. Our purpose in life is our own, it is what we make of it.
That's not bleak, that is not sad - that is something to be celebrated, and its wonderful.What I think is bleak, what I think is sad, is to spend your life worshipping a being for which their is no evidence, wasting your life in training and preparation for the supposed next life - one for which, once again, there is no evidence, no reason to suppose actually exists at all. That is a waste...