"Surely the Lord GOD does nothing, without revealing his secret to his servants the prophets" -Amos 3:7
"Despise not prophecies. But prove all things; hold fast that which is good." -1 Thessalonians 5:20
See also: "Signs of the Times"
What I am doing in the world today, -1975, Ralph Martin, St Peter Basilica, Charismatic Renewal.
The Gold of Precious Repentance, 1987, Fr. Francis Martin, New Orleans Charismatic Renewal
The prophetic messages of Mark Mallet
The Catechism teaches:
Throughout the ages, there have been so-called "private" revelations, some of which have been recognized by the authority of the Church. They do not belong, however, to the deposit of faith. It is not their role to improve or complete Christ's definitive Revelation, but to help live more fully by it in a certain period of history. Guided by the Magisterium of the Church, the sensus fidelium knows how to discern and welcome in these revelations whatever constitutes an authentic call of Christ or his saints to the Church. #67
It is clear that not even approved private revelations belong to the deposit of faith. Therefore they are not binding and we are not obligated to believe them. That being the case, why bother with them at all?
The answer is also in the Catechism: Their role is "to help live more fully by it (Christ's definitive revelation) in a certain period of history"#67. This is a very important role indeed, especially in times like ours when living the true faith is greatly opposed. We cannot afford to reject any help the Lord sends us to live more fully our faith. St Paul teaches us to be open to the Spirit and, at the same time, to be careful not to be fooled by the enemy. "Do not quench the Spirit, do not despise prophesying, but test everything; hold fast to what is good, abstain from every form of evil" (1Th 5:19-22).
Private revelation is not meant to tell us something new. Its role is to make present to us the truth already given in a way that alerts us of a particular aspect of it that we are ignoring. It serves to correct us and open our eyes. What good is God's revelation if we are ignoring it or if we are blind? Thus the importance of private revelation.