We must firmly grasp the deep interconnectedness of joy and suffering in order to understand the Calvinist doctrine traditionally known as “the perseverance of the saints.” People who are truly converted to God will never fully and finally turn back because God creates in them, by the miraculous power of the Holy Spirit, a love for him that is so powerful it perseveres through all trials. If we are true Christians, our love for God is unbreakable because God’s love for us is unbreakable, and his wonder-working power is always at work in us.
For the natural man, trials produce resentment toward God. For the new man, trials produce the joy of God because our love perseveres through suffering. The spirit of sin still has a presence in us, of course, but we now have a much more powerful Spirit planted in us by God’s love. No trial can ever break our love for God because the more trials we endure the more we get the joy of God.
An excerpt from The Joy of Calvinism. Forster, Greg. 2012. Wheaton, Il. Crossway.