This admonition was spoken to the apostles, and Peter in particular, following Peter's protest about the Master's impending trials. Jesus told Peter: "Get thee behind me," which was a stinging rebuke for him, and then he continued with this statement...relevant for serious followers of the Master in modern times, too!

158:7.5 After they had recovered from the first shock of Jesus’ stinging rebuke, and before they resumed their journey, the Master spoke further: “If any man would come after me, let him disregard himself, take up his responsibilities daily, and follow me. For whosoever would save his life selfishly, shall lose it, but whosoever loses his life for my sake and the gospel's, shall save it. What does it profit a man to gain the whole world and lose his own soul? What would a man give in exchange for eternal life? Be not ashamed of me and my words in this sinful and hypocritical generation, even as I will not be ashamed to acknowledge you when in glory I appear before my Father in the presence of all the celestial hosts. Nevertheless, many of you now standing before me shall not taste death till you see this kingdom of God come with power.”

158:7.6 And thus did Jesus make plain to the twelve the painful and conflicting path which they must tread if they would follow him. What a shock these words were to these Galilean fishermen who persisted in dreaming of an earthly kingdom with positions of honor for themselves! But their loyal hearts were stirred by this courageous appeal, and not one of them was minded to forsake him. Jesus was not sending them alone into the conflict; he was leading them. He asked only that they bravely follow.