In every age there are saints and sinners, people of great faith and those who live without it. Taking Jesus' command seriously to bring the Gospel to the whole world, the Church has consistently established missions throughout the world. With all the efforts of missionaries, religious, priests, and lay people, many have and continue to accept Jesus, but others remain as they were. The same happens in our families, neighborhoods, and work places. Good Catholics are proud to show their faith cheerfully without preaching and make our religion appealing. Yet, these efforts at evangelization fall on deaf ears.
The obstacle to divine grace is personal sin. If grace is blocked, then there cannot be an openness to receiving the Faith because Faith comes from God. It is His gift. Unrepented sins, as well as disordered passions, keep one closed within his self. People living this kind of life will deny truths that are plain to see. There is resistance to God's presence in their lives. God may give a special grace or grant a particularly beautiful inspiration, but these are stopped immediately. So, those who are wrapped up in their own pleasures will find it difficult to believe what God tells us.
This same attitude of resistance affects believers as well. Perhaps one is wavering in the Faith, or one is just going through the motions of believing. Personal sins weaken and damage our growth in Faith. Serious sins keep the Life of God from our souls.
The answer to all of this is honest, sincere, and complete confessions. Confession, also called Reconciliation, includes sorrow which also means a firm purpose of amendment. God cleanses the soul, and it is now able to and ready to receive the seed of Faith. We can do a great good by helping others to go to confession. Through it, not only are sins absolved but also other afflictions, such as doubts, are cleared up.