That's right, we are to love one another, which is exactly what I'm doing, otherwise I wouldn't care if brethren fall away from Jesus.
And truly... the doctrine of men that says we cannot sin anymore after having believed on Jesus is a way to fall away from Jesus, and instead be faced with His telling us to get away from Him when He appears on the last day...
Matt 7:19-23
19 Every tree that bringeth not forth good fruit is hewn down, and cast into the fire.
20 Wherefore by their fruits ye shall know them.
21 Not every one that saith unto Me, "Lord, Lord", shall enter into the kingdom of heaven; but he that doeth the will of My Father Which is in heaven.
22 Many will say to Me in that day, "Lord, Lord, have we not prophesied in Thy name? and in Thy name have cast out devils? and in Thy name done many wonderful works?"
23 And then will I profess unto them, I never knew you: depart from Me, ye that work iniquity.
KJV
Those are believers on Jesus. Notice they claim to prophesy in His name, and in His name cast out devils, and done many wonderful works. Yet Jesus shows He will reject them because they worked iniquity.
Does that mean those won't be saved eventually? Not up to us to decide. But based on what our Lord Jesus showed there, those won't be of His elect "first resurrection" reigning with Him per Rev.20.
Any doctrine that teaches that we cannot sin anymore after having believed on Jesus, and thus there is no need to repent and ask Jesus forgiveness, is a doctrine from men. It's a doctrine designed to lead brethren away from Christ, simply because refusing to recognize future sin, and failing to repent to our Lord Jesus, means being found with iniquity when He appears.