Trust in the Promises of God

Proverbs 22:6 is probably the most famous child raising verse in the bible, "train up a child in the way he should go, And when he is old he will not depart from it." This promise usually dies the death of a thousand qualifications under the weight of a few observations and real life experiences. Should it? What does it mean? Is it really a promise? If so, what kind of promise is it? Should I expect it's fulfillment, or doubt it? What should I do about it?