"Unless the LORD builds the house, those who build it labor in vain. Unless the LORD watches over the city, the watchman stays awake in vain" - Psalm 127:1
Whatever you set out to do, whatever you set out to achieve, whatever you aim to accomplish - it will be a vain effort unless God is with you.
Two reasons why this is so:
Firstly, God is the power behind everything - supporting and upholding it. He is in control of the many interactions and "chance" factors which could cause it to remain strong or to tumble, brokenly. If He doesn't provide for something to happen, it won't happen.
Secondly, God's will is absolute. If you go against His will then you will fail. That's not really in this text, but it is true of any endeavour we set out upon.
What does that mean for the Christian who seeks to be spiritual in everything they do? It means they will seek God's will in everything - learning the scriptures diligently, and reflecting on their life's experiences to interpret those experiences through God's words. It means that everything they do will be attempted under the cover of much prayer for God's help, both in wisdom of decisions and in upholding and producing the fruit of any effort.
If you are leading a family, you will lead in vain unless you seek God's will for your family and ask Him to make your choices and efforts fruitful. Business owners, students, mothers, teachers, pastors, missionaries, politicians, doctors, nations, governments... all need Him.