From John Calvin’s Institutes, book III, ch. 2, par. 20-21:
But it is especially our conscience itself that, weighed down by a mass of sins, now complains and groans, now accuses itself, now murmurs secretly, now breaks out in open tumult. And so, whether adversities reveal God’s wrath, or the conscience finds in itself the proof and ground thereof, thence unbelief obtains weapons and devices to overthrow faith. Yet these are always directed to this objective: That, thinking God to be against us and hostile to us, we should not hope for any help from him, and should fear him as if he were our deadly enemy.
To bear these attacks faith arms and fortifies itself with the Word of the Lord. And when any sort of temptation assails us- suggesting that God is our enemy because he is unfavorable toward us- faith, on the other hand, replies that while he afflicts us he is also merciful because his chastisement arises out of love rather than wrath. When one is stricken by the thought that God is Avenger of iniquities, faith sets over against this the fact that his pardon is ready for all iniquities whenever the sinner betakes himself to the Lord’s mercy.
Emphasis mine. I find this quote extremely comforting and I hope it is to you too. When we are faced with temptations, we often think the real battle is the battle to resist that temptation, a battle which we lose over and over. But Calvin here shows that the real battle is what comes after we give in to temptation, which is the temptation to think ourselves despised by God and under His wrath. This is compounded by the fact that God’s discipline often follows our failures, a discipline that we in our unbelief confuse with punishment. But punishment arises out of wrath, and discipline arises out of love, a distinction that makes all the difference in the world. When we confidently lay hold of God’s love for us, which He promises will never leave us, then we can be patient with and even rejoice in God’s discipline, knowing that only our good is in mind. We must constantly “betake [ourselves] to the Lord’s mercy.” The real battle is always the temptation to doubt God’s mercy and grace on the sinner.