My heart. my heart. Figure of speech Epizeuxis (App-6), as in Psalms 57:1. (See the Structure, above; also the Figure of speech Ecphonesis.)
fixed. steadfast. Contrast Psalms 78:37.
Related Commentaries of Psalms 57:7
Psalms 57:7
7 My heart is fixed,a O God, my heart is fixed: I will sing and give praise.