What do I pray when anxiety won't let me sleep?
Do not try to pray well at two in the morning. Use a few words and repeat them — the repetition gives the mind a floor to stand on. Say what you are afraid of, once, plainly, so it stops circling unnamed. Then hand the night over: I cannot hold this until morning, You can. If it is most nights, tell a doctor as well as God.
The phrase for this is menuchat hanefesh — rest of the soul, the quiet the heart is reaching for.
From the sources “In peace I will lie down and sleep, for You alone make me dwell in safety.” — Psalm 4