square one's shoulders

square one's shoulders (third-person singular simple present squares one's shoulders, present participle squaring one's shoulders, simple past and past participle squared one's shoulders)

1. To position one's shoulders back and in a straight line, forming a sort of square's edge.
2. (figurative) To prepare to deal with a hard task, to ready oneself for difficulty.
   • 2015 September 1, Sarah J. Maas, Queen of Shadows, →ISBN:

     Aelin squared her shoulders and slipped into the bejeweled crowd.