Ps 127 2 In vain you rise early
and stay up late,
toiling for food to eat-
for he grants sleep to those he loves.

In my opinion the first part of the Psalm is a curse in direct contrast to the second part which is "he grants sleep to those he loves"..which is the promised blessing. In this Psalm he is describing the care that God has for His covenant people in the midst of the humanistic ideal..which is to conclude that work is mans judgement. The principle is that God uses evil men to provide the nation who work 7 days a week, because they worship this world. We as Gods people push this view away.
The Psalmist is practicing pushing the cursed humanist away. In pushing it away he is establishing his success. This act of pushing the curse away by pronouncing the end of humanism is the defense that proceeds the use of weapons in war. This is why he says that unless the Lord builds the house....or unless Gods law is established in building the world by through the nation of Israel then the world would be humanistic.
When the Psalmist goes on to describe relationships in the family , he is saying that the curse against humanism will be the enforcement to simplify the family. Instead of the military being defined by public identity they will be defined by family origins. This involves the proper education of the children. So the teaching is that if we pronounce the curse against humanism then we will propagate children who defend the family values as the motive for fighting against the nations. The terrible effects of the curse are fueled by a very strong temptation to go outside of Gods law that simplifies and prevents humanism from being present from one generation to another. In this sense the success of the military in cursing the nations in war is spreading life on the earth.