Dictionary

inner strength en · NOUN

(idiomatic, uncountable, usually) Integrity of character; resoluteness of will; mental resistance to doubt or discouragement.
- To do as your aunt and uncle in their kindness wish, would, I am sore afraid, end in depriving you of the inner strength and happiness which God only gives to those who do their duty and try courageously to repair their errors. 1919 October, John Galsworthy, chapter I, in Saint’s Progress, London: William Heinemann, published December 1919, →OCLC, part III, 1 §, page 217:
- In any trouble, such as was this about the necklace, there would come over his face a look of weakness which betrayed the want of real inner strength. 1871 July – 1873 February, Anthony Trollope, “Mr. Dove in His Chambers”, in The Eustace Diamonds. A Novel, New York, N.Y.: Harper & Brothers, […], published 1872, →OCLC, page 126, column 2:
- First, it says the candidate has the inner strength or the wisdom or whatever it takes to address the unpredictable challenges he or she will face if elected. 2008 August 28, Michael Kinsley, “Everybody Knows the Trouble I've Seen”, in Time:

Spelling	Features	Labels	Source
inner strengths	Number=Plur		lexicographic