Many of us are like the man who ran up to Jesus and asked Him about everlasting life (Mk 10:17). We have kept the commandments since our childhood (Mk 10:20). We have been raised in a Christian family. Like the young man, we have "many possessions" (Mk 10:22). Also, we are not sure whether we have everlasting life.
Jesus says to each of us the same words He said to the young man: "There is one thing more you must do" (Mk 10:21). For each of us, there is a certain act of faith which would express our total surrender to the Lord. Jesus told the young man to sell what he had and give to the poor (Mk 10:21). Zacchaeus gave half of His belongings to the poor (Lk 19:8). Matthew quit His job (Mt 9:9). Francis of Assisi kissed a leper. The one more thing for you may be to evangelize, go to Confession, tithe, change your lifestyle, have "one more" child, forgive, apologize, get rid of your TV, quit smoking, read the Bible, go to Mass daily, home-school your children, fast and do penance, etc.
Have the love and courage to ask the Lord: "Is there one thing more I must do? If so, what is it?"