A good question dear. As you can see the meaning of the proverb is that man do whatever he wants to do and, in the end, it is in the hand of God whether He glorifies it or shatters it.
Same thing could be seen in "the gift of magi". Jim and Della bought presents for eachother by selling their valuable things but in the end their presents turned out to be futile because they are no more valuable for them as they sold their precious things for which the gifts were intended. it was quite unfortunate for them.
so as human being, the did their best but in the hand it is in the hand of God, the poweful.