Well generally speaking repentance isn't a one time thing. Not to mention ive asked those who continually preach OSAS did they only repent once after they were saved or throughout their lives got no answer. Confessing shows acknowledgement to wrongdoing and respect to God for sinning against him. If people get in the habit of believing "im saved so i dont have to address God regarding anything" that's pretty disrespectful imo.
We repent (change our mind) ONE time in regards to WHO Jesus is AND WHAT Jesus has done. So we confess He is Lord and He died for our sin, and He rose to life.
At THAT point we are BORN AGAIN. It is a NEW birth. A NEW creation.
We don't say "Yes Jesus is the ONLY Way for Salvation" Then say "No. There is another way, or I don't really need a savior".
Now the devil may try and and make you THINK you are no longer a son, but the Father still knows you are His, and He will always draw His children to Him. BECAUSE WE ARE HIS CHILDREN!
I simply can't understand why people don't get that we are Spiritually BORN HIS CHILD when we accept His Son.
The indwelling Holy Spirit will reveal to us what changes and sinful activities we need to turn from AND give us the ability to do it.