Now it is true that we should repent and stop sinning, but that is not how we will escape Hell. Therefore, escaping Hell is not the motivation for doing good. Once you have sinned you are destined for Hell, according to the Bible, and adding good works won’t change the fact that you’ve sinned. Some people think that if we added up all of our good works and our evil works, God would accept us if only our good works were more in quantity and quality than our evil works. But that’s not how the God of the Bible thinks. No amount of good works can erase the fact that you have done evil... your good works do not atone for your evil works. Once you have sinned, your situation is hopeless. That is, except that Jesus Christ, who was sinless, voluntarily died on our behalf, and His death was sufficient to atone for our sins. Understanding how that works is, I think, something that is ultimately beyond our comprehension, and so it must necessarily be accepted by faith. But believing that this is true, God counts that belief as your righteousness (to put it in the phrasing of Romans 4).
So a Christian’s motive for good works, if they understand this, cannot be to escape God’s wrath. They know that doing good instead of evil won’t save them because they have already done enough evil to receive the punishment of Hell, and they continue to do so by nature. Rather, what happens is that, when a person accepts Christ they receive the Holy Spirit who begins to transform that person’s life so that they begin to naturally hate evil and love righteousness. Christ’s nature starts to manifest itself in us. Not entirely, however, else we wouldn’t sin at all. God’s plan is to give us our full “transformation” when He returns. So we do continue to live in a fallen world with a broken, sinful nature. And God could leave us completely unchanged until His return if He wanted to, but He gives us this “taste” of what is to come. It is this change in us which often serves to assure us that what we have is real, because after all, faith is difficult when you have a broken, sinful nature.
So we don’t perform good works out of fear, but rather out of love! Christ’s nature is one of love, and if Christ’s nature is manifest in us, then our love for others is all the more amplified because of that. And love, if you think about it, is really the basis for all true, or genuine morality. We do good not out of hope for reward, nor to save ourselves from punishment... our reward is assured and our salvation is assured. As people of faith we still sin because the time for our full salvation has not yet come. But we have this altered nature, as I said before, so that we don’t deliberately want to sin. When we slip up it is generally met with regret and repentance shortly after. If a person claims to be a Christian but doesn’t appear to live this way... that is, they deliberately sin often and have no regrets about it, it may be a sign that they are not genuinely saved at all.
But we’re in this fallen state where we are susceptible to sin, though our final relief from our sin nature is guaranteed us. Why God does this is something I think we’ll better appreciate looking back, but in the present it’s a struggle. Sin has its appeal, but we know that it’s no good for us. I think that any true Christian will tell you “What I really long for is the time when I won’t even be tempted to do the wrong thing any more!” But this struggle between hating sin and yet also seeing it’s allure and being tempted, this state of affairs is itself the punishment for our sins. Sin is, by nature, destructive, and so sinfulness itself can be used by God as a punishment. But the final judgment of mankind will come at the return of Christ, and at that time the final punishment for sins will be dealt, as well as salvation for those who have trusted in Christ’s atonement for them. This future time is what we wait for; to finally receive deliverance from sin and corruption.
The LORD is good to those who wait for him, to the soul who seeks him. It is good that one should wait quietly for the salvation of the LORD. … Why should a living man complain, a man, about the punishment of his sins? (Lamentations 3:25-26, 39)