he is not capable of breaking promises, unlike many of those people we trust most. So when Jesus swore an oath to his disciples that he would build his church the confessing of Christ as laid out in the scriptures, and that the gates of hell would not prevail against it, he was incapable of saying something he actually wasn't sure of or somehow knew it wasn't true.

That's actually a good way to spend some time, if you read through the gospels of the New Testament, make note of all of Jesus' teachings and interactions. What is remarkable is how his intentions, words, and ability to back up his words are united and unbroken. He never says one thing and then backtracks it or has second thoughts. We take this for granted but we're so used to people saying grand things but with asterisks, footnotes, fine print, and the basic inability to follow through.