Unless the Lord builds the house, its builders labor in vain. Unless the Lord watches over the city, the watchmen stand guard in vain (Psalm 127:1 NIV).
We need God. The truth is as simple as that. When the Master Builder Solomon says it we need to take note. And when Solomon who never faced a foreign invasion during his reign and had rest from his enemies says it we need to take note.
The first image that is used here is that of the process of building. A house needs a plan. It needs a foundation. It needs materials. It needs laborers. Yet a building is never complete without God building it. Solomon is not just talking about buildings here. He is talking about our lives itself. We should be careful how we build our lives. We should make sure that our lives are built upon the sure foundation, God Himself. Instead of imposing our thoughts, we can ask God what His desire is concerning our lives. And if we allow Him, He will gladly build it all for us. Otherwise, we will be building in vain. That is a sad waste of time, talent and resources. So allow God to build your life and future. Then it will provide you with comfort and shelter. Moreover it will be beautiful.
The second image used here talks about guarding the city. This is important for within it is your house. As long as we live on earth, there will be invasions from enemies. So building alone is not enough. Keeping it safe from attacks is important. And that requires constant watch. But even there, you need God. For if you think you will stand watch, who knows whether you will be able to detect all enemy movements! When you stand watch you only know the enemy movement when it has reached you. But when God watches over you, He knows enemy movements even when it begins. He will warn you and keep you safe. So let God keep watch over you for if you stand alone at the watch it will be in vain.