Most of the answer exists in the previous question, but I would have to ask anyone who has this attitude to truly look at their lives. I doubt anyone who is honest with themselves, including the greatest saints, would ever dare to say that they did not have room for improvement.
All would agree that they could have lived their lives better and more perfectly. Our time on earth is a great opportunity to do good. It is a great opportunity to earn merit. Once we die, this opportunity is gone. The graces offered to everyone who asks with an open heart in Medjugorje, will change their life. The graces will strengthen you in your faith, and bring you to a closer relationship with Jesus and His Blessed Mother. There is no refuting this. It is simple truth.