In Proverbs 14:23, he says 
There is profit in all labour,
In any situation of life,
 marriage, career, business, 
raising children etc,
>if you apply the principle of 
diligence which involves acquiring
deep  knowledge and applying it persistently in the different areas of your life you will see profitable results. Hence if you are not getting rewarding profits in the different areas of your life, you have not been diligent enough.