Peter doesn't say: Ignore your worries. He says: Cast them on God. That's an active process. You take what burdens you and consciously hand it over. Why? Because he cares for you. Not because you deserve it, but because he loves you.
Worrying is often an attempt to keep control. But in the New Covenant, you can let go because someone else carries the responsibility. Not indifference, but trust.
Today: Actively cast one worry onto God and leave it there.