When going gets tough, the tough get going

सम्पत्सु महतां चित्तम् भवत्युत्पलकोमलम् ।
आपत्सु च महाशैलशिलासङ्घातकर्कशम् ॥

- नीतिशतकम्

In times of prosperity, the minds of great people are as soft as gentle water lilies, whereas in adversity when going gets tough, they become as hard as a huge mass of solid rock.

When going gets tough, the tough get going.
Intelligence is the ability to adapt to change.