Its a good saying. It reminds you not to get off balance by success. Another good saying is before enlightenment chop wood carry water, after enlightenment chop wood carry water. The point is the same. No matter how great things are going keep you head. Its like when your having sex, let your enthusiasm get the better of you & its all over. 
"Most of the change we think we see in life is due to truths being in & out of favor." ~ Frost