If you know God, and his greatness, and his wrath, holiness, justice, wrath, grace, you will tremble in his presence. This is not something you grow out of. This is something the immature grow into - including our kids.
To a certain extent, obedience is a matter of reason and discipline. I rationally decide that I want to obey and act accordingly.
However, this obedience is limited. It will take me only as far as I can follow with my reason and with my effort.
How can obey God, at anytime, in any circumstance?
Only if I trust in him, only if I love him. How can I trust and love God?
When you consider the deep meaning of each line of the Lord's prayer, you will realize that there is no better prayer that the one the Lord Himself taught us, and be awed at how it covers all the crucial areas.
Be careful to obey all these regulations I am giving you, so that it may always go well with you and your children after you, because you will be doing what is good and right in the eyes of the LORD your God. (Deuteronomy 12:28)