2 Corinthians 4:16

16 Therefore we do not lose heart. Though outwardly we are wasting away, yet inwardly we are being renewed day by day.

Read 2 Corinthians 4:16 Using Other Translations

For which cause we faint not; but though our outward man perish, yet the inward man is renewed day by day.
So we do not lose heart. Though our outer self is wasting away, our inner self is being renewed day by day.
That is why we never give up. Though our bodies are dying, our spirits are being renewed every day.