Is there a proper, Christian use of the memory of my (repented-of) sin?

I received this very important question from a dear brother, who often finds himself mulling over his past sin, grieving over how he cannot appreciate the infinite weightiness of it. As is often the case, it's a question whose answer would be useful to many, even though it is the first time I can remember having been asked. Here's the beginning of an answer:

I'd be delighted for this to be a face to face conversation, but am also glad to give enough synopsis to provide a little relief. 

There is therefore now no condemnation to those who are in Christ Jesus, who do not walk according to the flesh, but according to the Spirit.Romans 8:1

Brethren, I do not count myself to have apprehended; but one thing I do, forgetting those things which are behind and reaching forward to those things which are ahead,  I press toward the goal for the prize of the upward call of God in Christ Jesus.
Php 3:13-14 (admittedly, contextually, talking especially about any 'good' in our past)

We certainly must never dwell upon repented-of sin in any self-condemning way! If God "forgets" our sins in that manner, and we decide that we will continue to remember them, not only do we harm one of His dear children, but we make ourselves out to be wiser or holier than God!! I​n the face of such texts, we need biblical warrant to dwell upon the past at all. And we do have it.

This is a faithful saying and worthy of all acceptance, that Christ Jesus came into the world to save sinners, of whom I am chief. However, for this reason I obtained mercy, that in me first Jesus Christ might show all longsuffering, as a pattern to those who are going to believe on Him for everlasting life. Now to the King eternal, immortal, invisible, to God who alone is wise, be honor and glory forever and ever. Amen.
1Timothy 1:15-17

Here is an especially helpful passage, because it gives not only warrant for remembering the past but also a biblical aim for doing so. I often hear v15 quoted, but without highlighting its relationship to vv16-17! We may make a right use of the memory of the greatness of our sin: 

(a) as a trophy of Jesus' patience with us, in order to encourage us about how He might save others; i.e. not so that we would have woeful thoughts of ourselves, but that in the face of the infinite gravity of others' sin, we would be yet more impressed with the mercy of Christ and not consider anyone else hopeless, and certainly not look down upon anyone.

(b) to be driven to great eruptions of praise to God

After all, our lives are all about God's glory--and particularly that glory as displayed in Jesus.

This has been the Holy Spirit's great work in all of creation and redemption: literally to shine light upon the glory of Jesus as God's chosen display of His glory for all time and into eternity [Shameless plug for listening to the morning sermon from the 23rd if you haven't yet--one of the best sermons (I think) that the Lord has enabled me to preach upon the Holy Spirit]. Whatever is good in us is by and from the Holy Spirit. And so we can expect that all "good" remembering of our sin will have this as its aim: shining light upon the glory of God in Jesus Christ.

Now, taking that doctrine into the realm of more directly answering the question of "how much" or "how heavily" we should remember our past sin: just as much as is conducive to and actually producing of overflowing effusions of praise of the glory of the grace of Christ!

The force that must be applied by these memories is not a weight that makes our heads to hang, but an upward pull that lifts our faces in praise.

Personally, without the aid of sins already committed, I continually produce enough new sin to end up confessing it, rejoicing in God's redeeming me in Christ, and praising His ongoing mercy and patience. 

So, the only reason I would make intentional reference to my former sin would be when working on humility toward an unbeliever who appears particularly hard, or working on encouragement about the possibility of his salvation, or working on gratitude and praise to God for His entire redeeming work from election to atonement to justification to sanctification and glorification.

And however unintentional memories of former sins arise in my mind--whether by the Holy Spirit or an angel or an accusing devil/demon or Satan himself--I seek (though imperfectly so) to employ that memory unto such biblical ends as above.

Not having made recent study of this, I would guess that there are other texts that present us with other biblical uses for remembering repented-of sin. But we can continue that conversation face to face. 2Jn v12.

Grace and peace,

Pastor