Based on reading the quote by Thomas S. Monson "Obedience is the great test of life"  I infer that he has been tested on obedience everyday of his life. I believe its true because everyday people get the decision to choose the right or wrong way. Furthermore people decide to be obedient because it always comes with a better or positive outcome than choosing the wrong. To add I think that  a lot of people should live by these words because they might make choices that they might regret at that time. But if your being obedient to something negative its better not to be because thats just peer pressure and you dont want to follow steps that might leave on bad thoughts. Also sometimes these words may be the extra push people need in order to do greatness that wouldn't be able to be accomplished on their own.