What is the purpose of life?

In my spiritual practice, one consistent question i used to ask was - If the origin and the destination of the universe are predetermined, then why do zillions of beings lead minuscule lives for zillions of years? What is the point of the circle of life? 

The answer I got was complex and simple at the same time - If the blood in your body always has to remain at 5-6 liters, why do zillions of RBCs circulate for 180 days each? What is the point of their circle of life? 

The point of that circle of life is to keep you alive. You - who are both an organism and an ecosystem. Everything - from the quark to the multiverse, is both an organism and an ecosystem. And an ecosystem is a living, breathing entity. Every element must complete its journey. That circulation - that is life. Consciousness is often compared to a grain of light. The circle of life is necessary because the universe is not wood, diamonds, and rock. It is consciousness. The only carrier of consciousness is the tiny entities at various stages of awareness. They are ALL necessary to ensure that the universe remains ever-new. We cannot forget selfishness or base traits - they are integral to consciousness too. Like photons are charged particles that carry light from point A to point B, beings are sentient particles that ensure that Consciousness remains in the Universe. 

Why is suicide prohibited in every single religion of the world? Because lives are not incidental. Each life has a mandatory journey that it has to complete. Think of it as being in a grade in school. You can drop out of second grade because it is too hard. But will they put you in third grade? No. They will tell you to take your time, drop a year, two if you want. But when you rejoin, it is going to be second grade only, not third grade. 

It is exactly the same with births. You can choose to end a birth early. You can also take time in the time space. But when you take a physical birth again, it WILL be for the same lessons. For the same objective that your soul had set out originally. 

It is your timeless soul that sets its path. It decides how much or how little it will do in each birth. Like a grain of light, it reaches the destination (which Hinduism calls Nirvana). 

Remember the endless pillar of light that Shiva showed to Brahma and Vishnu? That is our existence. That is the journey of the universe. No beginning and no end. 

If you take a picture of the sun or the moon at the exact same spot for a year and super impose the pics, you will find that they make a symbol known to men and mathematicians. The symbol is infinity. Let that sink in - infinity is a loop. 

That is the spiritual answer to your question - what is the purpose of life. If we have to die anyway, why live? The RBCs have the answer. We are all photons.