The purpose of life is undoubtedly to know oneself. We cannot do it unless we learn to identify ourselves with all that lives. The sum-total of that life is God.
We can speak very much to the purpose and yet in such a way that the whole world cries out in contradiction: namely, when we are not speaking to the whole world.
It is worthwhile for one to make an effort to achieve happiness. Just as the purpose of a plant is to grow, so it is that the main purpose of every human being is to survive and to grow until death.