Psalm 127 tells us that if God is not in the building of our houses they will not stand.  We can work all we want but it is the will of God that finally determines whether our efforts will amount to anything other than our own exhaustion.  Does this lead us into fatalism?  Does it mean that we should throw up our hands and say it does not matter what we do?  Here is an answer from Charles Spurgeon:

"Note the Psalmist does not bid the builder cease from labouring, nor suggest that watchemen should neglect their duty, not that men should show their trust in God by doing nothing: nay, he supposes that they will do all that they can do, and then he forbids their fixing their trust in what they have done, and assures them that all creature effort will be in vain unless the Creator puts forth his power, to render second causes effectual.  Holy Scripture endorses the order of Cromwell - 'Trust in God, and keep your powder dry': only here the sense is varied, and we are told that the dried powder will not win the victory unless we trust in God.  Happy is the man who hits the golden mean by so working as to believe in God, and so believing in God as to work without fear."

(From the Treasury of David on Psalm 127)