Once when Jesus was praying alone, with only the disciples near him, he asked them, "Who do the crowds say that I am?" They answered, "John the Baptist; but others, Elijah; and still others, that one of the ancient prophets has arisen." He said to them, "But who do you say that I am?" Peter answered, "The Messiah of God." He sternly ordered and commanded them not to tell anyone, saying, "The Son of Man must undergo great suffering, and be rejected by the elders, chief priests, and scribes, and be killed, and on the third day be raised." Then he said to them all, "If any want to become my followers, let them deny themselves and take up their cross daily and follow me. For those who want to save their life will lose it, and those who lose their life for my sake will save it.
To be a Christian requires daily self-denial. It would be a great mistake to think we can go longer than a day without denying ourselves somehow, without feeling the liberating weight of the cross.
Of what does this self-denial consist? Never having a real home for ourselves in this world (Luke 9.57-58); following Christ and his mission even above the demands of family (Luke 9.59-62); loving him more than family and even our own lives (Luke 14.25-26); dispossessing ourselves of all worldly goods (Luke 14.33).
Furthermore, self-denial consists of removing from our hearts all those evil tendencies which have grown in us through the common ancestry we have in the disobedience of our first parents. The desire to have power over others, to be recognized, to steal, to envy, fight and complain, and in general the tendency toward anything on the list of death. (Galatians 5.19-21)
But above all, the preeminent form of self-denial is to do God's will, not our own. In this, the perfect example is Mary. "Here am I, the servant of the Lord; let it be with me according to your word." (Luke 1.38) She gave away her entire life so God could walk among me.