The one who makes himself as little as a child is the greatest in the kingdom of heaven. The Church commemorates today St. Therese of the Child Jesus, popularly known as the ‘Little Flower of Jesus.’ St. Therese entered the Carmelite convent of Lisieux at the age of fifteen (she had to obtain a special permission from the pope to enter a convent at that age) where she lived a life of humility and complete abandonment to the Lord. She died of tuberculosis at the age of 24, making her one of the Church’s youngest canonized saints. She is the patroness of the missions, of florists, and of France; secondary patroness of the Apostleship of Prayer. St. Therese was proclaimed doctor of the Church by Pope John Paul II.
St. Therese lived a short life. But in the nine or so years that she lived as a member of the Carmelite community, her manner of life endeared her to her fellow nuns. She embodied the virtue of humility in the way she lived her religious vows (the path of humility is the “little way” which, in her autobiography,  The Story of a Soul,she urges all to follow). And even as her health was slowly being eaten away by tuberculosis, she remained steadfast in her faith and we are told that she never complained even once about her suffering. 
In the Gospel passage for today, the apostles approach Jesus with a question about the greatest in the kingdom of heaven. It was a question that perhaps had been developing ever since the moment Jesus started preaching about the kingdom. Their inquiry might have been motivated by ‘selfish’ reasons since greatness is something that we all want to acquire (the mother of the sons of Zebedee would later on approach Jesus asking him to reserve the best seats in his kingdom for her sons [cf. Matthew 20:20-23]). In his response, Jesus proposes to them another way of thinking about greatness. He tells them that to be considered great in the kingdom of heaven, one had to let go of every ambition that seeks to put one above others. In the kingdom that he came proclaiming, greatness is achieved by those who remain children in their relationship with God and with their fellows. Those who are considered great in the kingdom are those who abandon themselves totally to God. They are great those who refuse to outgrow their dependence on God as well as their connection to their brothers and sisters. 
St. Therese is considered great today because she remained a child of God even in her suffering. She did not let anything destroy her relationship with God. To her, God was still God no matter what she was going through. God remained to her the loving father who knows how to give good gifts to his children.