Some Christian writers have claimed it’s unnecessary for Christians to ask for God’s forgiveness since all our sins (pre- and post-conversion, past and future) were forgiven when Christ said “It is finished” (John 19:30). But two scriptures seem to contradict this: Jesus’ model prayer instructs us to pray for forgiveness for ourselves (Luke 11:4), and he says in Matthew 6:15 that God will not forgive us (assuming “us” refers to believers, as he is addressing his disciples) if we do not forgive others. When do you consider that we are truly forgiven, at the cross or when we confess our sin (1 John 1:9)?
I think it’s frankly obnoxious to teach that we don’t have to ask for forgiveness when we sin. One follower of one of these writers you mention carried it so far as to make a personal vow that he didn’t ever have to say “I’m sorry” or “Please forgive me” when he hurt anyone because after all, his sins were forgiven at the Cross! (Need I elaborate on what that did to his marriage and family and workplace relationships???)
There is a difference between knowing we were forgiven at the cross, and experientially RECEIVING that forgiveness after we sin. It’s like the difference between standing at the bottom of a waterfall, thirsty, with our cup upside down. . . and turning the cup right side up to receive the water.
Forgiveness was offered to everyone at the Cross, but we don’t experience it until we confess our sins and receive it by faith (turning our cups right side up). The question of when we are truly forgiven depends on if you’re looking at it from God’s perspective or from ours. God-wise, we were forgiven before we even knew we needed forgiveness. Man-wise, we are forgiven when we receive it.
Also, receiving forgiveness afresh when we sin is what reconnects our broken relationship with God and with others. Confession and forgiveness are intrinsically related to fellowship and intimacy.
Hope this helps!