"when obedience becomes our goal it is no longest an irrational instead of a stumbling block it becomes a building block."
 I think it means that obedience is the number one thing in life and key to everything and that it becomes a block by that it means that were getting better and building better and building means to get stronger and taller. For example when i obey i get benefits from it. When i obey my parents they get nicer and give me money and respect me but,m if i dont i get no respect and they get angry and loose money because they will take away my money and benifits from me like my phone and ps4 so thats why you always obey someone no matter what they tell you. never argue just obey. In order to live a happy life you must obey thats just how it is. If you disaobey bad stuff will come to you so watch out.