The LORD bless you from Zion! May you see the prosperity of Jerusalem all the days of your life! May you see your children's children! Peace be upon Israel!
There are four distinct blessings for the worshiper of The Lord. The first is that God would bless through worship. The "souvenir" of a trip to Jerusalem to worship at the temple was the real blessing of God upon the worshiper.
The second blessing was for Jerusalem itself to prosper, thus ensuring a lifetime of secure worship there. It is the blessing of continuous worship.
The third blessing was for a long life and a full family. It is the request to see healthy grandchildren and to know full circle the blessings of God in another generation.
The fourth and final blessing in Psalm 128 is for the peace of the nation. This is not so much a national security prayer as it is a hope for the true peace of God to pervade hearts and lives that obey The Lord and love His law.