For every action, there is an equal and opposite reaction ~Sir Isaac Newton (25 December 1642 – 20 March 1726/27)

While there is no clear answer in the sky for the causes or reasons of our existence, this much is abundantly obvious. Before existence, there was nothingness . This nothingness was a state of natural balance , one may think of it as the number zero - not specifically positive or negative , but the point of the middle. No one or thing had come before or after it, all that is or was, being non-existent. That was until, existence was thrust into that nothingness. There will never be an answer to why exactly existence came into being, but what is means is clear as day. This, by virtue, created something that was the opposite of nothing - this is akin to addition, in that the way life acts as a variable (x) . The moment life came into existence, so too did a lack of life- Death came into being. Death , by its very nature, serves to reinstate non-existence . Death can also be viewed as subtraction, taking away from that which is already present leaving only a lack of something. In this view, the opposite of life is negative or bad. Therefore, the meaning of life must be the continuation and expansion of life for as far as we are concerned - we are all that is out there, nothing has nor will ever be what we are or similar . For this very reason we should must keep going no matter the cost , do not rob life of your existence . There will never be another you in this existence. Though life is mired by hardship and loss, one must continue to spread the miracle that is life . For if the gift were not spread, nothingness would return and that had been, or has yet to be done will be for naught. In this regard, Life gives meaning to existence . The causes or justification for the harmful or indifferent nature of existence towards life goes as follows. All that does exist, was made without the consideration of sustaining or supporting the creation of life , by these terms one can denote existence, as one which is hostile to all that is living. Despite the harsh nature of existence, life found a way to come into being, and we are the product of such a grandiose event. Therefore, we must not let the gift die out. Life is the light to the darkness that is existence . Like a single lit candle in a vast dark and empty space. And if life is be snuffed out, then still we should not stop. Do not go softly but fight tooth and nail against the darkness. We must fight- with all of our might- to prevent the dying of that light . And if life is be snuffed out, then still we should not stop, if anything we should fight harder. Do not go softly but fight tooth and nail against the darkness.

Regarding the confusing nature of the date [thonyc.wordpress.com]) Newton died.
The quote being from The Principia Mathematica , which notes Newton's third law of motion. Though the law in context discussed motion, it may be applied to the question of everything.