I'll put my big-girl hat and give it a shot. As you well know, however, I don't represent all believers.
Jesus did not write down his teachings. He gathered a small group of followers and they learned at his feet, as it were. He then sent them out to practice what he preached. I would say then that a Christ-like life is learned by example not just by way of writing.
So how have these teachings come down through the ages? By way of example and word of mouth, one Christian to another.
I also personally think that Jesus has changed through the ages to suit modern mores. He drinks and curses less, and loves more.