… casting all your anxieties on him, because he cares for you. (1 Peter 5:7)
There is a promise suited to every sin you are tempted to commit and every form of unbelief that takes you off guard and makes you anxious. For example:
When I am anxious about being sick, I battle unbelief with the promise, “Many are the afflictions of the righteous, but the Lord delivers him out of them all” (Psalm 34:19). And I take the promise with trembling, “knowing that suffering produces endurance, and endurance produces character, and character produces hope, and hope does not put us to shame, because God’s love has been poured into our hearts through the Holy Spirit who has been given to us” (Romans 5:3–5).
When I am anxious about getting old, I battle unbelief with the promise: “Even to your old age I am he, and to gray hairs I will carry you. I have made, and I will bear; I will carry and will save” (Isaiah 46:4).
When I am anxious about dying, I battle unbelief with the promise that “none of us lives to himself, and none of us dies to himself. For if we live, we live to the Lord, and if we die, we die to the Lord. So then, whether we live or whether we die, we are the Lord’s. For to this end Christ died and lived again, that he might be Lord both of the dead and of the living” (Romans 14:7–9).
When I am anxious that I may make shipwreck of faith and fall away from God, I battle unbelief with the promises, “He who began a good work in you will bring it to completion at the day of Jesus Christ” (Philippians 1:6); and, “He is able to save to the uttermost those who draw near to God through him, since he always lives to make intercession for them” (Hebrews 7:25).
So, let us make war, not with other people, but with our own unbelief. It is the root of anxiety, which, in turn, is the root of so many other sins.
So, let us fix our eyes on the precious and very great promises of God. Take up the Bible, ask the Holy Spirit for help, lay the promises up in your heart, and fight the good fight — to live by faith in future grace.
From Desiring God’ Solid Joys Future Grace, page 59