I'd like to add Rom 3:25 - 'sins that are past'.
The idea that all sins have been paid for through Christ's death on the cross, is quite different from 'all sins have been forgiven'.
To be forgiven, a sinner (whether an unbeliever or a believer), has to come to the Father through Christ (our Advocate) the Son, in just the same way (although, perhaps with greater speed, prior assurance of forgiveness, and less of the sense of a great leap into the unknown), as at that first repentance for sin.
I do think that if there is an understanding that we have been planted/grafted into the death of Christ on the cross (co-crucified with) Him who destroyed him who had the power of death (Heb 2:14; Isa 27:1 - where 'sea' = 'people'), then individual sins which occur after salvation are much easier to deal with.
I can't apologise that this is a recurrent theme in my postings, and it is mainly so because it needs to be as deeply embedded in current Christian doctrine, as it is in Paul's letter to the Romans, ch 5 and ch 6.
For further reading on the Old Testament shadow, I recommend Ron Bailey's old thread 'Propitiation and the Red Heifer', which, if translated into the common Christian wilderness experience, ('Egypt' being taken out of the hearts of God's believing people), may be a helpful picture of how readily the Christian is to receive cleansing - 1 John 1:7.
There is also, Heb 12. The famous first verse, could, I think, be more carefully translated with respect to the verbs. According to Berry's Interlinear, it is 'having laid aside' and, 'the sin which is easily surrounding us'. This expression of the Greek, keeps the pressure of sin [u]external[/u], as with the temptations to which James refers (Jam 1:14, 15), and Paul in Rom 1:26 (vile [i]affections[/i]), and Gal 5:24.
The fact is, that if we sin knowingly, we cannot claim ignorance (Acts 17:30, 1 Tim 1:13, Num 15:28, Deu 19:4), and we have, in effect, rejected Paul's plea in Gal 5:1. We will find ourselves in bondage. It is incumbent upon us to embrace wholeheartedly, a genuine change of heart, so that we do not [i][b]desire[/i][/b] (will to) sin.
This challenge is what finds us out, much to our chagrin and at times, despair. But, there [u]is[/u] genuine hope in abandoning ourselves being dead in Christ, from which the power to walk in newness of life can arise. (Rom 6:4)
Furthermore: Rom 8:13, 1 John 3:3, 1 John 5:21. Note the emphasis on what 'we' have to 'do' as a demonstration of our heart's desires. The Holy Spirit is our [u]Helper[/u], only.