Two attitudes towards suffering

We see in Lourdes two attitudes of Divine Providence with regard to human suffering that can appear to be contradictory.
On one hand, the thing that attracts the most attention at Lourdes is that Our Lady has pity on men, hears their requests, and works miracles to free them from the pain and illnesses they suffer. Also, Our Lady has pity on souls, and to prove that the Catholic Faith is the only true religion, she often works spiritual miracles of conversions. By making both physical and spiritual miracles, she shows that she is our Mother who loves us and wants to relieve us from suffering both here and in eternity.
On the other hand, we see something else at Lourdes. A great number of sick people go to Lourdes and return without being cured. Why does Our Lady give cures to some, and not to others? In fact, there is an important lesson for us in the cures she doesn’t give, and perhaps the greatest miracle of Lourdes is found precisely in this.
For the great majority of persons, suffering is indispensable for their own sanctification. Therefore, the illnesses and troubles they suffer are necessary. It is through sicknesses and spiritual tribulations that they will sanctify themselves. One who does not understand the role of suffering and sorrow in bringing about detachment, conversion, and love of God does not understand what the spiritual life really is.