Fortitude
Etymology
From Latin fortitudo, "strength, firmness," from fortis, "strong, brave." Another of the cardinal virtues, it originally covered physical strength as much as moral resolve. English has narrowed it toward the inner sense: not muscle, but the toughness that lets a person keep going.
noun · /FOR-tih-tood/
Steady courage and strength of mind in the face of pain, danger, or prolonged difficulty.
What it names
The endurance kind of courage — the capacity to bear hardship over time without collapsing or giving up.
Example
It took real fortitude to sit through two years of treatment and still show up for others.
Related idea
Courage often names a single brave act in the face of immediate danger; fortitude is the slower virtue of enduring hardship that does not end.