What can repentance be compared to?
Joel Beeke explains in this video that repentance can be compared to a soldier marching in one direction and then doing an abrupt about-face and marching in the opposite direction. Similarly, when God saves a person, there is a new birth and that sinner leaves his old life behind. You leave the old life and sin no longer has dominion over you.
This is a lifelong change. This is not just a one-time event in the life of a Christian. You keep striving after godliness and repenting for sin throughout your entire life.
2 Timothy 2:22 (NKJV) - "Flee also youthful lusts; but pursue righteousness, faith, love, peace with those who call on the Lord out of a pure heart."