John 14:29 And now I have told you before it come to pass, that, when it is come to pass, ye might believe.
Jesus told them things before they happened so that they would know He knew. He could only know the future if He were God. He made it clear to them that the reason He was telling them was so they would know that He had known and was God.
We have His Word about the beginning. We have His Word about our past. We have His Word about our salvation. We have His Word about our future. I know He knows and that I can trust Him.