Being sustained means to be provided for, supported, protected, and defended.
Cast your burden on the Lord, and He shall sustain you. He shall never permit the righteous to be moved.
Psalm 55:22 NKJV
The word “permit” indicates permission so we can thus accept that God must give permission for the righteous to be moved.
We can therefore understand that nothing will happen to God’s children, unless He allows it.
God promises us in His Word, His protection, guidance, and sustainability.
Trust in God for He will protect you always.