He is telling us that we must continually strive to please God in all we do and in how we live.
Let me use another analogy to make this point clear. If you eat breakfast on Monday, you have energy that carries you to about noon. But if you do not eat lunch, you will be run down, tired, and famished by dinnertime. To keep your body running at peak performance, you must need a continual intake of food, which provides energy to your body.
You cannot receive Jesus ‘back then’ and never again pursue more of Him in your daily life. You must have a continual intake of Christ into your heart, and that provides the salvation we so desperately need.