Casting is an action verb.
People who fish (not me) know that casting is not passive. As I Googled images of casting, I found people in athletic stances, forcefully launching their line into the Deep.
Here we're told to CAST our anxiety...our cares in some translations...fling it upon the Lord.
Waiting for the anxiety to simply vanish on its own has not worked for me. I have to muster my spiritual might to claim this verse and actively entrust my cares to Him who cares for me. Casting, believing, trusting...all ACTION.
Lord, give me the grace and faith and spiritual strength to cast my cares on your boundless, loving shoulders.