Anything done, apart from the Lord, is done in vain. It is pointless and a waste of time and energy. Only things done for the Lord have any lasting impact or value.
Our work (v 1) has no value apart from the Lord.
Our tendency to worry and fret and try to fix things ourselves (v 2) serves no purpose. We must lay our burdens at His feet.
Our family – parenting, marriages, etc – (v 3-5) must be grounded in the Lord and his Word.
May it all be for your glory, Lord.