After the amazing "mountain top" experience of the transfiguration, Jesus, Peter, James, and John return to the base of the mountain to find Jesus' gospel movement in crisis. The other nine disciples created a scandal for Jesus when they couldn't drive out a powerful demon from a man's son. Jesus gets the job done. In the process, he teaches a crucial lesson about what it means to be his followers. Disciples can follow Jesus and do the good works of his way only by prayer.
In this passage, Jesus explains to the twelve disciples, and to the crowds gathered with them, that a genuine disciple must "deny himself, take up your cross, and follow me," (v. 34). He says this in the context of his own path to Jerusalem and to the cross that awaits him there. So, any genuine Christian heeds this calling from the Lord to take "self" off the throne of our hearts and let Jesus be there; to embrace the path Jesus calls us to walk, which is often shamed by this world; and to stay the course to our last breath.