The most dangerous aspects of sin are the ones we don’t readily identify as sin at all! It is their ability to “hide out” that makes them the most dangerous.
The beauty of God's plan for we believers is that, while we never lose saving faith, He continues to add to our faith (implies we are lacking). The Apostles were no different.
If you reject His gifts, His grace, then you will lack the ability to love Him back the way He wants us to love Him! You will also lack the ability to love others the way Jesus loves you!