Heb 6:3-8
4 For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit, 5 and have tasted the good word of God and the powers of the age to come, 6 and then have fallen away, it is impossible to renew them again to repentance, since they again crucify to themselves the Son of God, and put Him to open shame. 7 For ground that drinks the rain which often falls upon it and brings forth vegetation useful to those for whose sake it is also tilled, receives a blessing from God; 8 but if it yields thorns and thistles, it is worthless and close to being cursed, and it ends up being burned. NAS
Rev 3:4-6
5'He who overcomes shall thus be clothed in white garments; and I will not erase his name from the book of life, and I will confess his name before My Father, and before His angels. 6'He who has an ear, let him hear what the Spirit says to the churches. ' NAS
Back sliding and apostasy are not the same concept.