Therefore being justified by faith, we have peace with God through our Lord Jesus Christ: Romans 5:1
Peace is both the absence of conviction over unforgiven sin and the assurance that we are reconciled with God.
Peace cannot be reduced to a subjective emotional feeling; it means that the hostilities have ceased (v. 10; 8:7) and that we no longer fear God's wrath (v. 9). -Vic Reasoner, Commentary on Romans, 182.
But peace also includes the emotions. F. F. Bruce said that peace and joy are twin blessings of the Gospel and then quoted an old Scottish preacher who said, "Peace is joy resting; joy is peace dancing." - F.F. Bruce's Commentary, 6:120.
Lloyd-Jones warns us that there is a false peace and gives 5 Indicators of a False Peace:
1. It is characterized by an intellectual assent to certain truths.
2. They rest in their own faith rather than the work of Christ.
3. They are too glib and do not show adequate concern for their shortcomings.
4. They are interested only in forgiveness and not in righteousness.
5. They take sin much too lightly. - Assurance, Romans 5, pp. 24-25, quoted by Reasoner
Truly as Joseph Sutcliffe exclaimed, "Justification is never alone; all the graces follow in clusters, with privileges of the highest order." (Commentary 2:453) Great peace is just one of these many blessings! Praise God! - Phillip