Kennedy Hall explains in an outstanding video
John 6:66-69
Because of this many of his disciples turned back and no longer went about with him. So Jesus asked the twelve, “Do you also wish to go away?” Simon Peter answered him, “Lord, to whom can we go? You have the words of eternal life. We have come to believe and know that you are the Holy One of God.”
I can't recommend enough this video by Kennedy Hall. There is much wisdom shared by him. (I can't begin to match his words.) In addition, if you haven't read his book, "SSPX - The Defence", (yes, defence) it's the best book I've read regarding SSPX and the confusion Pope John Paul II created.
(Kennedy Hall is a contributing editor for OnePeterFive. He is the author Terror of Demons: Reclaiming Traditional Catholic Masculinity and Lockdown with the Devil, a novel published by Our Lady of Victory Press. He is a writer at Catholic Family News, LifeSiteNews and is the host of the Conservative talk-radio show, The Kennedy Report. He is married with four children and lives in Ontario, Canada.)
God Bless you