Just like all external sinful words and deeds are first internal sinful thoughts and desires (James 4:1; Mark 7:20-23), so all external good behaviour is first internal good character. We sin from the inside out, and we also transform into true righteousness from the inside out (Rom 12:2).
David was chosen as the righteous replacement of wicked king Saul because David, though handsome on the outside, was righteous on the inside (1 Sam 16:6-12).
The noble accomplishments of the Proverbs 31 lady sprung from a sincere heart filled with a fear of the Lord (Pro 31:30). Likewise also the holy wife of 1 Peter was noticed more for her gentle and peaceable nature than her behaviour—as respectful as that was (1 Peter 3:2-4).
This is why, when the Apostle Paul wanted to see godly practices among the saints, encouraged them first to godly thinking (Phil 4:8-9). This is also why some of the most practical instructions in the Scripture come after a mental exercise in what we believe from within (compare Eph 1 – 3 with 4 – 6 and Romans 1 – 11 with 12 – 16).
In the words of Titus 3:8-9, be insistent on Gospel truths, then devote yourself to godly behaviour which is profitable. Similarly do not preoccupy yourself with nonsense, because that in turn will produce corresponding worthless behaviour.
You sin from the inside out; you also grow in holiness from the inside out.