" When obedience becomes our goal, it is no longer an irritation; instead of a stumbling block, it becomes a building block " 

                         I think what this quote is saying is once we realize that obedience is something really important , then it would be really helpful and would keep us up , not stumbling. It is always important to be obedient do matter what. If your'e not obedient, bad things would happen . With obedience, that would take us to a whole knew level. You don't want to interfere with the stumbling blocks . Stumbling blocks like drugs , smoking or being rude will just bring you down. The building blocks would be a new amazing thing. Building blocks like being honest , loyal , patient and respectful will lead you to having a great future .