It becomes increasingly clear to me that Catholicism simply can't be understood without the well-established doctrine of Mary being sinless. After all, if there is such a creature who is perfectly free from sin and perfectly devoted to our Lord Jesus Christ, this means that the only standard we are to strive for is this same sinlessness and perfection. Indeed, the aim of every saint over the ages has been exactly this - to die sinless or as perfectly free from sin as possible.
This has stunning implications for every aspect of spiritual life - it means that if we don't view the eradication of our sins and the attainment of sanctity as the only true evidence of our salvation as members of Christ's Church, we're in danger of falling into some kind of heresy. For Mary herself wasn't only preserved from the stain of Original Sin, but throughout her life she always chose to turn her back on sin and temptation, and always chose the way of perfect obedience to God. Of course, no other creature before or since has been born free of Original Sin, but the choice to live completely free from sin - or as close to it as possible - is always ours to make, and on this basis we are very much in the same boat as the Blessed Mother. Or to put it in more practical terms: Mary herself never lived a single moment of her earthly life with the thought, "I'm saved, so it's okay if I don't fully resist the temptation to sin if it arises, and I don't really have to deny myself - spiritually as well as physically - in order to avoid the near occasion of sin."
Consider this simple fact: If Mary had wilfully sinned or had even an inclination to sin, she would've blocked the salvation of the human race and the redemption of the entire universe via her baby Son! Not that this would've stopped the fulfillment of God's plan, but can you imagine how horrible a price Mary herself would've paid?
Which leads to the crucial point: the closer and more intimate our relationship with God, the more our sin will expose us to the very fires of hell.
One doesn't have to be Catholic to have this understanding of sin and salvation: but if this isn't at the very crux of the Christian life on a daily basis, well, one runs the risk of not fully appreciating what sin is - and therefore not fully appreciating what mercy is. It sounds very unloving to many if not most Christians that God demands such absolute perfection from us, because it's so much more soothing to think that Christ's death for us is sufficient and all we have to do is believe in Him, and our sins will automatically be washed away. But of course, the reality begs to differ: the more we try to be right with God and serve Him worthily, the more our total depravity shows up and renders ourselves unfit to see Him face-to-face. Am I just trying to pull everyone down? Absolutely not - I am obliged before God to pray that everyone I know and meet will attain sanctity and perfection ahead of myself. But if this is how we're obliged to pray for one another, we can't be wishy-washy about the awful truth of how despicable and deserving of hellfire our sins are, even so-called "small" sins.