Revelation 21:
6 And He said to me, “t is done! I am the Alpha and the Omega,
the Beginning and the End. I will give of the fountain of the water of life
freely to him who thirsts.
7 He who overcomes shall inherit all things, and I will be his God
and he shall be My son.
Scripture is pretty clear that after salvation we are in a spiritual war with Satan Ephesians 6:12, and Paul also makes clear that after we have been saved, there is a continuing conflict between our wanting to walk in the flesh, (that wants us to live in sin)- and our desire to walk after the Holy Spirit that now dwells in us - and Paul warns that choosing to live in sins (works of the flesh), will keep us out of heaven:
And Jesus warns a church in Revelation to repent, and tells them if they overcome, He wont erase their names from the book of life:
Rev 3:3 Remember therefore how thou hast received and heard, and hold fast, and repent. If therefore thou shalt not watch, I will come on thee as a thief, and thou shalt not know what hour I will come upon thee.
Rev 3:4 Thou hast a few names even in Sardis which have not defiled their garments; and they shall walk with me in white: for they are worthy.
Rev 3:5 He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels.
And this is the church that is claimed to be the reformed Church, yet Jesus starts off warning them they are dead, that most of them had defiled their white robes (which represent being righteous), and warned to repent - ending by telling them if they overcome, their names will remain in the book of life.
Overcoming is after salvation, and there’s no guarantee we will be an overcomer.