For the self there is never birth nor death. Nor does the self ever cease to exist. The self is unborn, eternal, ever-existing, undying, and primeval.
~Bhagavad-gita 2.20

If you erroneously identify yourself with your body, you will conclude that your existence will end with the destruction of your body. But if you know that you are the eternal self within the body, you know that your existence will not end when your body dies.

Your body has a beginning and an end; your body is subject to birth and death; but you, the spark of life within the body, are eternal. You have no beginning, nor will you have an end. The material body will cease existing, but you will never cease existing.