饮水思源

I saw this in a school I visited today, 饮水思源. 
It has a lot of meaning for me personally because my mother always taught my brother and I since young that we must always 饮水思源 which literally means when we drink, we must think of its source. In plain words, it means that we must be grateful for our blessings, never take things for granted and never forget one's origins.