One of the distinctions I made in Unpacking Forgiveness: Biblical Answers for Complex Questions and Deep Wounds was that while we should always have an attitude of forgiveness, this doesn’t mean that we should always forgive. A discussion has been taking place over at the Desiring God blog about this very point. A.B. Caneday is quoted as saying:
If we tell others, "I forgive your sin" even though they refuse to acknowledge their sin, we remove the very incentive the gospel places upon them to confess their sins and to seek forgiveness. If we take preemptive action by granting forgiveness of sin to those who do not repent, on what basis could the church ever follow the procedures of Matthew 18:15-17?
There is a proper biblical or gospel order. We are to imitate God. God forgives the sins of those who repent (cf. 1 John 1:9). Likewise, we must always grant forgiveness to those who repent (cf. Luke 17:3).
In Mark 11:25 Jesus calls us to be forgiving. Scripture requires us to distinguish between being forgiving, which is the virtue of always being ready and eager to forgive, and the act of forgiving, which is the actual remission of the sin done against us. Thus, as God is always forgiving, which means that he is eager and desirous to forgive, and as God forgives those who repent, so godliness/Christlikeness is to be and to do the same.
You can read Caneday’s article, A Biblical Primer and Grammar on Forgiveness of Sin.