Psalm 13: "Why Rock-bottom is a good place to be."

Ps 13:5~6
"But [in spite of...] I trust in your unfailing love;
my heart rejoices in your salvation.
I will sing to the Lord,
for He has been good to me."

David calls out in frustration... how long!?
How long before God answers? - before salvation comes?
But after 4 verses of making his frustration known to God, he hits "rock-bottom."
~ meaning... he comes to the "Rock of Ages" at the bottom of his life. And having a sure foundation - a foothold - unshakable ground... that compels him to sing and rejoice... in spite of all that is happening around him.

God - You are my rock, my sure foundation... my trust is in You ~ for all other trusts fail...