Everything you are right, but you cannot justify about planned sin after knowing Christ, if someone willfully planned doing their sin after knowing the truth, then its like like against the salvation. Your emphasize should be on repenting, but not on forgiveness for planned sin after slavation.
Heb 10:
26-29 26 For if we keep on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a certain fearful expectation of judgment and a fury of fire that is about to consume the adversaries. 28 Anyone who rejected the law of Moses dies without mercy on the testimony of two or three witnesses. 29 How much worse punishment do you think the person will be considered worthy of who treats with disdain the Son of God and who considers ordinary the blood of the covenant by which he was made holy and who insults the Spirit of grace?