Sins are Not finite and discrete - therefore they are un-countably numerous

It is probably a consequence of the legalistic notion of religion (e.g. The Ten Commandments specifically and the Hebrew Law generally) that there are specific categories of sins, and that Men in their lives will commit a certain finite and (in principle) countable number of these sins. 

This then suggests that there must (sooner or later) be some kind of reckoning of sin; whereby each Man must be evaluated and compensate for the specific sins which he has committed. For instance; I have heard it said that after death a Christian must (in some way or another) be confronted by, and account for, each and all of the sins he committed during mortal life.

But this is wrong; because sins are in truth a consequence of our nature and that of this world. They are the degree by which we diverge from a complete harmony with God's creative purpose. 

This divergence, this failure to live-by-love, is not a matter of X number of specific acts; but instead a matter of every Man having (to lesser or greater degree) a wrong orientation, wrong motivations, wrong gratifications etc. 

Sin is the consequential totality of being-wrong and going-wrong, of divergence from the divine.  

Some Christians talk as if they themselves, or most other people, are Basically Good; and commit just a few sins per day/ month/ year. And they are able to think like this because they only count Big Sins (e.g. breaches of the Ten Commandments, or Canon Law), and completely ignore (or accept as inevitable hence 'natural' - hence they 'don't count') the innumerable instances of (for example) spite, fear, dishonesty, resentment, lust, despair etc; which everyone experiences every day - indeed every waking (or dreaming) hour. 

But that is a wrong description of the human condition. Each of us comes into the world as an unique Being and into an unique family and social environment; and we make an unique set of choices. 

And all of us are, to a significant degree, un-aligned with the 'perfect' life which would be lived entirely by love...

Sometimes we do come into harmony, and therefore we experience to some degree what a Good life is like; but inevitably we will soon steer or drift "off course" again. All who are capable will experience the Good in order that every such person can know it, and then potentially choose Good; after death when given the opportunity to follow Jesus Christ. 

Eternal resurrected life in Heaven is the perfection which we mortal beings on earth cannot attain: indeed, the fact that it is unattainable is exactly why Heaven is necessary; and why Jesus Christ was mortally born and did his work of salvation: so that we - like Him - could attain to Heaven via death.    

After death we are not - therefore - confronted with, and called to account for, our sins understood as a sequence of discrete phenomena that must individually repented. The situation is Not a double-negative of cancelling sin. I see things the other way around, almost. 

What we are confronted-with is the positive and unitary choice of whether to follow Jesus, and be admitted to Heaven - this, on condition of leaving-behind anything about us that is inconsistent with that wholly-loving reality. 

One who loves Jesus, and loves God enough (a Saint, perhaps), or even one who desires to be in Heaven unconditionally because of those deceased that he loved and who love him who are already there (and, aside, I think that contact with the beloved resurrected dead will be apparent at that point) - such people will make that decision for Heaven quite easily. 

But others may find that there is some particular "thing" about himself that he is reluctant to "give up", some "blockage" that stops him from making the choice of Heaven. 

This is known as his besetting sin. 

Then a particular and discrete choice may arise that corresponds to a particular and specific "sin" in the more traditional sense. Then we will be confronted with the need to repent that besetting sin which blocks our access to Heaven* - and it will be made clear that we must give-up that part of our mortal selves if we are to live eternally "in Love". 

In sum: the choice of Heaven is not understandable in terms of repenting every one of a large number of particular sins; because that is a wrong way to understand sin. In reality, our sins are uncountable, because they are not categorical and because they are so integral to our being and this world. 

However; many people apparently have a broadly-categorical besetting sin (or more than one) that, unless repented, will block the decision to choose salvation. And such specific sins may indeed need specifically to be confronted and repented.  

*Note: This was, for me, helpfully depicted in CS Lewis's The Great Divorce. h/t - A recent comment by Mia triggered the above reflections.