Although the doctrine of Perseverance only makes sense in the context of monergism (Calvinism), it is commonly believed by many synergists (Arminians & semi-Pelagians) as well. Parents of ungodly children seem especially prone to employ “eternal security” as a soporific for their grief, clinging to that day long ago when their child “asked Jesus into his heart.” But perseverance means more than “once saved, always saved.”
The fifth point of the doctrines of grace is preserving grace. It is often referred to as the perseverance of the saints or eternal security. Others speak of this doctrine by means of the pithy phrase “once saved, always saved.” This is the biblical truth that all those who have been brought to faith in Christ will never be lost. But this doctrine is about more than eternal security. It also includes the lifelong perseverance of the believer in the pursuit of godliness. While the doctrine of election reaches back to eternity past, this doctrine—preserving grace—reaches forward throughout the entirety of one’s Christian life and into eternity future. This doctrine simply establishes that all those chosen by the Father, redeemed by the Son, and regenerated by the Spirit will pursue holiness and be kept secure in Christ forever. The preserving grace of God rests upon the immutability of His sovereign grace to save His elect forever.
—Steve Lawson, Foundations of Grace (Reformation Trust, 2006), 434–435.