Why do we believe in the Holy Trinity? Because to know the Son is also to know the Father and this inner knowledge comes from the Holy Spirit. Anyone begotten by God is a child of God. His knowledge of God comes from above. With the seal of the Holy Spirit in him, it is almost impossible for him to deny God. Once we are sealed with the Holy Spirit, we always want to please God. We do not want him to ever leave our side. We enjoy his presence in us so much that we pray a lot, we try to love like Jesus and try to be as generous as possible. To be a son / daughter of God is an honor and a joy.
In the Gospel reading, John the Baptist understood his mission well. He was to lead others to the Messiah, to prepare their hearts for the coming of Jesus. In our lives we are often so busy preparing to get rich, successful or powerful. We prepare our children to do the same. Yet Christ wants is to prepare for the coming of his kingdom.
Christ wants us to work for peace, justice, righteousness and selflessness, values which our world sorely lacks.