I do believe in an eternal existence after this earthly life. I cannot prove it. There is no solid proof.
The only thing we have is faith and a belief of the promises made in the Bible. If you have no faith, there is no proof that can be produced to convince you.
Some will say because there is no proof, then the belief is false. I have seen too many miracles in my life not to believe there is a better life waiting for us.