Are the Buddhist sutras 100% verified if applied in life?

I remember my teacher mentioned this in class : > "Do not believe in anything simply because you have heard it. Do not > believe in anything simply because it is spoken and rumoured by many. > Do not believe in anything simply because it is found written in your > religious books. Do not believe in anything merely on the authority of > your teachers and elders. Do not believe in traditions because they > have been handed down for many generations. But after observation and > analysis, when you find that anything agrees with reason and is > conducive to the good and benefit of one and all, then accept it and > live up to it." Does that mean that the sutras are 100% correct if I follow them? because it is very confusing, or according to what siddartha mentioned, I can't even trust the sutras when he says do not believe?