Comments on Psalm 55

"David's experience of a false friend is extremely moving, and reminds us of the poignant experience of Christ.  
Fear (v v1-8), fury (v v9-15) and faith (v v16-23) may be said to characterize the psalm.  
'Fear only leads to desire for flight. 
 Fury only emphasizes the consciousness of wrong. 
 Faith alone creates courage'" (G.Campbell Morgan)

from The Complete Book of Psalms for Singing by Roland Ward.