Paul actually left one step out here; he could have added sanctified. Sanctification is the period between justification and glorification during which we become holy, when the growth takes place.
Everything in regard to this issue exposes a process. We are to consider ourselves pilgrims heading toward the Kingdom of God, gradually being transformed into the image of God along the way. The qualities of character, whether human or godly, are not produced instantaneously but through the everyday gathering of information, weighing it, making the necessary choices, setting our wills, and watching to see the results.
Even as Israel had to walk out of Egypt and across the wilderness to the Promised Land—or there never would have been a change in their situation—so must we live this process to grow to become like God and be in His Kingdom. The laws of God are written on our hearts (Hebrews 8:10; Jeremiah 31:33) by life's experiences while we have a relationship with God. Like everything else in life, it is a process that has a beginning and end.
Like every educational system, it moves from simple to complex. It moves from that which is clearly stated in the letter of the law to what is less apparent and depends upon a background of instruction, experience, and results. It depends on faith in and love for God and love for man that have grown in a person to aid him in properly understanding, applying, and practicing the spirit of the law.