Mercy and Grace are often confused. While the terms have similar meanings, grace and mercy are not the same. To summarize the difference: mercy is God not punishing us as our sins deserve, and grace is God blessing us despite the fact that we do not deserve it.
Mercy is deliverance from judgment. Grace is extending kindness to the unworthy.
According to the Bible, we have all sinned (Ecclesiastes 7:20; Romans 3:23; 1 John 1:8). As a result of that sin, we all deserve death (Romans 6:23) and eternal judgment in the lake of fire (Revelation 20:12-15). With that in mind, every day we live is an act of God's mercy.
If God gave us all what we deserve, we would all be, right now, condemned for eternity. In Psalm 51:1-2, David says, "Have mercy upon me, O God, according to thy lovingkindness: according unto the multitude of thy tender mercies blot out my transgressions. Wash me throughly from mine iniquity, and cleanse me from my sin."
A plea to God for mercy is asking Him to withhold the judgment we deserve and instead grant to us the forgiveness we in no way have earned. We deserve nothing from God. God does not owe us anything. Anything good that we experience is a result of the grace of God (Ephesians 2:5). Grace is simply defined as unmerited favor. God favors, or gives us good things that we do not deserve and could never earn. Rescued from judgment by God's mercy, grace is anything and everything we receive beyond that mercy (Romans 3:24).
Common Grace refers to the sovereign grace which God bestows on all of mankind regardless of their spiritual standing before Him, while saving grace is that special dispensation of grace whereby God sovereignly bestows unmerited divine assistance upon His elect for their regeneration and sanctification.
Mercy and grace are best illustrated in the salvation that is available through Jesus Christ. We deserve judgment, but if we receive Jesus Christ as Savior, we receive mercy from God and we are delivered from judgment.
Instead of judgment, we receive by grace salvation, forgiveness of sins, abundant life (John 10:10), and an eternity on Earth with God personally and directly.
“And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God”. Revelation 21:1–3
Because of the mercy and grace of God, our response should be to fall on our knees in worship and thanksgiving.
"Let us therefore come boldly unto the throne of grace, that we may obtain mercy, and find grace to help in time of need."