a repeated line in Psalms 42 and 43.

It was, for its time, a "hot lyric", or better still, one of those themes that the pastor king repeated for his people.

"Why art thou cast down, O my soul?  and why art thou disquieted in me?  hope thou in God: for I shall yet praise him for the help of his countenance." -PS 42

"Why art thou cast down, O my soul? and why art thou disquieted within me?  hope in God: for I shall yet praise him, who is the health of my countenance, and my God." -Ps 43

So God is the key to a good mindset, we not only emulate God's calm demeanor and strength, but we petition Him and give praise.  We get our own #mindset from God Himself in the end.

"O send out thy light and truth: let them lead me; let them bring me unto thy holy hill, and to thy tabernacles."