"when obedience becomes our goal,it is no longer an irritation:             instead of a stumbling block it becomes a building block."
                                                             
                                                                   by James E. Faust
This statement means that when you are already very obedient not get irritated because you're doing the right thing for example: when your parents tell you to do something or they need you, you get mad and do not obey because you get irritated when they ask you for things to do when you're doing your stuff, but when you obey you feel good and if you keep obeying no longer makes you difficult and irritating obey and that moment you are building.