I remember reading Psalm 13 a few years ago when I was in some of the darkest moments of my depression and anxiety. I remember reading verse one then actually praying those words and meaning them: "Will you forget me forever?" I know that might be rough to hear, but that's how I felt. I felt as though I was my own worst enemy, and God wasn't doing anything to me fight me.
I also remember reading down to verses 5 and 6: "But 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."
I thought to myself, "Wow, I am SO not like David at all." Think about it, here is David being chased by his best friend’s father who was trying to KILL HIM, and he was praising God; he was CHOOSING to sing. This is the art of lament.
Lament is not about complaining and whining about your circumstance. Lament is a form of worship that honestly admits to God the pains of your heart with the knowledge that if God is who he says he is, your prayers will be answered and your joy restored. Through his words, David taught me (and I’m still learning this every day) that even while we feel pain we must choose worship; we must will ourselves to cry our hearts out to God. After all, it is in our prayers of lament that God hears us; it is in our prayers of worship that we hear him.

Psalm 13:1-6