The Crab and its Mother

A Crab said to her son: "Why do you walk so one-sided, my child? It is far more becoming to go straight forward." The young Crab replied: "Quite true, dear mother; and if you will show me the straight way, I will promise to walk in it." The mother tried in vain, and submitted without remonstrance to the reproof of her child.

Example is more powerful than precept.

Nobody likes it when you ask them to do something that you can’t even do yourself. Before making unreasonable demands, it’s a good idea to be able to do that thing first. Then you won’t feel stupid for making people do something that’s impossible.