One of the reasons our God may not make a sick person well is so the person does not lose his reward in the afterlife. This is similar to a father not giving all of the inheritance to his children at once so they don’t go on to waste it. We should always consider this and the afterlife as a continuum then we can understand that God may have plans to reward us in the afterlife.
https://www.koinoniaorthodoxias.org/gerontes/riseis-gerontos-paisiou/
From the book “From the Ascetic and Hesycastic Athonite Tradition” Translated by Anna Pipinos and Elias Pipinos.
