The mind should be of steel

The mind of the upright man ought not to be like wax, or any other soft material, which always yields to the shape of what presses on it, and is stamped with its form and impress and keeps it until it takes another shape by having another seal stamped upon it; and so it turns out that it never retains its own form, but is turned and twisted about to correspond to whatever is pressed upon it.

But the righteous man should instead be like some stamp of hard steel, that the mind may always keep its proper form and shape inviolate, and may stamp and imprint the marks of its own condition on everything that happens to it, while nothing that happens to it can leave any mark on the stamp.

Based on Saint John Cassian

A monk carrying the cross of Saint Constantine the Great