Grace, in the biblical understanding, does not merely add a supplement to our efforts; it fundamentally dismantles and overturns the entire framework of self-reliance. It exposes human striving as ultimately futile in spiritual terms, revealing that no human effort can achieve or maintain true righteousness before God. Instead, grace redirects all glory and praise to God's sovereign initiative. As you rightly cite Paul’s testimony in 1 Corinthians 15:10—“But by the grace of God I am what I am, and his grace toward me was not in vain. On the contrary, I worked harder than any of them, though it was not I, but the grace of God that is with me”—this encapsulates the biblical paradox: all aspects of existence—identity, ministry, and labor—are rooted in grace, yet this grace energizes diligent service rather than leading to complacency. It is a divine empowerment that motivates effort without boasting in self. This understanding aligns with your point that grace inverts the self-effort paradigm. It makes God's favor the sole foundation of our identity and actions, rendering boasting and self-congratulation impossible. 

Theologically, this is reinforced by Paul’s assertion in 1 Corinthians 15:10, where he attributes all his work and identity to grace: “But by the grace of God I am what I am… yet not I, but the grace of God that is with me.” Paul’s life and apostolic labor are entirely grace-sourced; this grace empowers diligent effort without the illusion of merit. John Piper echoes this idea, stating, “The power of God’s grace produces incredible industry; dependence is the objective, weakness is the advantage,” capturing the paradox that true strength and productivity in the Christian life come through reliance on divine grace, not human strength. This theological perspective profoundly challenges the life of security based on self-systems. Instead, it points us to trust in God's paternal, unearned favor—adopted as sons and daughters through grace (Romans 8:15-17)—which sets us free to love others authentically and generously. Grace received flows outward as self-forgetful giving—of time, resources, and even one’s very life—thus transforming our motives from self-interest to divine service. Paul’s writings in Philippians 2:17 and 2 Timothy 4:6 provide vivid illustrations of grace’s culmination in sacrificial service. Paul describes himself as being “poured out as a drink offering” upon others’ faith and service—a vivid picture of self-giving that glorifies God rather than oneself. 

Martyn Lloyd-Jones highlights that Paul’s martyrdom was “a pleasure to God,” illustrating that grace manifests in poured-out devotion, modeling the believer’s life as a continual offering of self in gratitude and service. God’s generosity is complete and unmerited; He gives everything freely, then rewards acts that are empowered by grace (Hebrews 6:10). All glory ultimately belongs to God because salvation, sanctification, and every good work are His gracious gifts. The believer’s life becomes a continuous oblation—a pouring out of oneself—not to vindicate oneself but as a testament to the triumph of grace over self-effort. While this path demands surrender and complete dependence on divine grace, it also yields profound liberty, security, and joy rooted in God's unwavering favor. The reflection profoundly and insightfully highlights the radical reversal that divine grace brings to human understanding of righteousness, effort, and self-reliance. It underscores how, in our fallen state, mankind instinctively constructs a moral ledger—an internal "checkbook" of sorts—where worth is measured by effort, achievement, and the deservingness of reward. This paradigm manifests in a wide array of pursuits: the pursuit of comfort, financial stability, predictable routines, and a sense of moral self-sufficiency. It is rooted in autonomy, pride, and the belief that one can earn favor through personal merit—an approach that diametrically opposes the gospel’s core message: that true righteousness, salvation, and transformation are gifts bestowed solely by God's unmerited grace, not earned by human effort. 

In summary, divine grace radically redefines the human experience of righteousness and effort. It dismantles the false security of self-reliance, replacing it with the liberating truth that salvation and transformation are gifts from God. This truth invites believers into a life of humble dependence, joyful service, and unshakable assurance—an existence rooted entirely in the unmerited, sovereign favor of our gracious God. The doctrine of salvation further emphasizes that grace alone initiates and sustains the Christian life. Ephesians 2:8-9 succinctly states, “For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast.” This underscores that salvation is entirely a divine gift, not something earned or deserved. John Calvin underscores this by affirming that human inability to do good is so profound that even our best efforts are marred by sin unless renewed by grace. Psalms 108:12 O Lord, grant us strength against our foes, for mere mortal aid is but ashes in our hands."Without God's grace, even acts that appear outwardly virtuous are spiritually worthless. The assurance of God's unchanging favor serves as a vital catalyst for transformation. 

When believers are made confident of their secure status in Christ, they are naturally motivated to grow into His likeness—“being changed from one glory to another”—a process rooted in divine grace, not human effort. The union with Christ, central to Reformed thought, ensures that sanctification is a work of grace that conforms believers to His image through the Spirit’s ongoing work. This theme is central to Reformed theology, which insists that grace is sovereign, efficacious, and transformative. It overturns the natural man’s "moral compass," which is inclined toward self-sufficiency. The doctrine of total depravity affirms that, without divine grace, human effort is inherently corrupted and incapable of producing true righteousness. Even outward acts of goodness, when performed apart from grace, lack genuine spiritual value because they originate from self-love, not love for God. 

Jonathan Edwards, in his Treatise on Grace, elaborates on this distinction by differentiating unbelievers grace—those external restraints and moral influences that restrain sin in the unregenerate—from saving grace, which involves a supernatural infusion of divine love that reorients the soul from self to God. Edwards emphasizes that without this divine intervention, even the seemingly good deeds of the unregenerate are deficient because they lack the divine motive and origin. Progressive sanctification—the ongoing process of becoming more like Christ—is also a gracious work of God. 2 Corinthians 3:18 illustrates this: “And we all… are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit.” The transformation into Christ’s likeness is not achieved by human effort but by divine action through the Holy Spirit. Charles Hodge emphasizes that this divine agency is the true cause of sanctification, not human striving, further reinforcing the centrality of grace in spiritual growth.