What I've learned that seems most helpful to people is to clearly distinguish forgiveness from reconciliation. Some folks assume that both are the same thing. They aren't. Forgiveness is what *I* do; Reconciliation is what *we* do. Forgiveness has to do with releasing a debt caused by behavior; Reconciliation has to do with re-building broken trust.
Forgiveness is also an event (or a series of events in which forgiveness becomes more complete); while Reconciliation is a always process. What I mean by that last statement is this:, forgiveness is something we do because we have come to a kind of crisis, realizing we must forgive, and so we do. In that way there is a process involved, but the act of forgiveness is a single act, or (more often) a series of acts of forgiving. Reconciliation, on the other hand is by nature a process through which, over time, trust is rebuilt. It is not an 'act' of the will so much as a step-by-step restoration of something broken.
When people think that forgiveness=reconciliation they balk (rightly!) at forgiveness, because forgiving someone doesn't fix the relationship. They're right about forgiveness not fixing the relationship! And they're wrong about forgiveness being the same thing as reconciliation. On the other hand reconciliation cannot happen without forgiveness.
One more thing we must say about forgiveness: if it seems 'fair' to forgive, it's not forgiveness, it's only recognition that we were wrong about being/feeling hurt, or wrong to hold on to the hurt. It's only forgiveness when the other person doesn't deserve to be forgiven, when the hurt was/is real, and we have a 'right' to feel as we feel. The kind of forgiveness that denies the reality or intensity of someone's sin against me, or a loved one, diminishes the nature of forgiveness, and drives the hurt down deeper, where it festers in our spirit. No. It's only forgiveness if we know that the person has no right to it.
As far as repentance goes, that's a hugely different topic. The only thing I want to say about that is that without the empowerment of the Holy Spirit, we can't fully turn from and be free from habitual sin. We are 'slaves to sin' until the Spirit sets us free. This is our human nature (our "flesh"). The desires of the flesh must be killed, but they can only be killed as we are empowered by the Holy Spirit to do it (Rom 8:12).
If you look at the connection between Rom 7:7-25 and Rom 8:1-17, what we see is that when I try to do it (count the 1st person singular pronouns in Rom 7:7-25, vs Rom 8:1-17; better yet, look at them in the original language!), I fail; when the Spirit enters the picture, success becomes possible. In other words, trying harder doesn't work; yielding to and relying solely on the Spirit who lives within me is my only hope to defeat enslavement to a particular sin.
Most strategies offered in churches, and by Christian counselors about secret or habitual sins, has to do with managing the sin, rather than defeating its hold on us. We want to improve our record from resisting 80% of the time, to 90%, as if that's what repentance is. Over time, we all know, it doesn't work, and it certainly doesn't set us free, any more than telling a slave that he's free for 90% of each day--he's still a slave isn't he?
We, in the Reformed tradition, believe in the sanctifying power of the Holy Spirit. Our confessions drip with the power of the Spirit to make us more and more holy. But when it comes to secret or habitual sin, we try to fix ourselves? The phrase "You foolish Galatians" comes to mind; human effort just won't do.
So, what do we do then, if trying harder doesn't work? There are only three things we can do that have any chance to give us progress: Ask, Seek, Knock. In other words, pray like our spiritual life depends on it; pray alone, with others, receive prayer ministry. Don't do this alone! We really do need each other here, and praying with others is more effective (Matt 18:19). Expect that, while such deliverance can be instantaneous (and sometimes is!), often the healing comes in 'layers.' Also realize that as the Spirit empowers, *we apply* that power to our own hearts and lives -- at least that's my experience, both personally and with others. Yes, there is a bit of mystery here, and it's difficult to put into words. Yet, there's no other way.