We only see 10% of an iceberg because the other 90% of it is submerged. People's hearts are similar. For instance, if you lied in an uncomfortable situation, then there must be more to it than just the lie. It may well be because you have evil in your heart such as the heart of untruthfulness, a benefit-seeking heart, a heart of deceit, or a heart that makes excuses to justify behavior. You can change your heart to be holy and good only when you look to your inner self, not your outward appearance.
"YOU SHALL BE HOLY, FOR I AM HOLY." (1 Peter 1:16)