Psalm 42:10 (ESV)

10 As with a deadly wound in my bones, my adversaries taunt me, while they say to me all the day long, “Where is your God?”

The worst thing for the poet is that his enemies keep saying, Where is your God? In doing so, they declare God to be powerless. They keep on saying, that God you rely on cannot really help you. This mockery cuts through his soul; these insults keep gnawing at him. These vicious words are unbearable to him. This was also the case with King Hezekiah in later times (see 2 Kings 18:19–25 and especially 2 Kings 19:14–19). God’s children cannot bear to be told that no help is to be expected from God. That mockery pierces them to the very bone; it is like an incurable wound within them.