In Mere Christianity, C.S. Lewis wrote:
You may remember I said that the first step towards humility was to realise that one is proud. Conviction of sin comes only from God’s Holy Spirit, and self-pride is indeed sinful. I want to add now that the next step is to make some serious attempt to practise the Christian virtues. That is, after accepting God’s conviction of your sin, confessing it back to him, and trusting Christ for your justification and salvation. A week is not enough. Things often go swimmingly for the first week.
Call this the “Honeymoon Period.”
Try six weeks. By that time, having, as far as one can see, fallen back completely or even fallen lower than the point one began from, one will have discovered some truths about oneself. No man knows how bad he is till he has tried very hard to be good.
That’s because sin is our natural condition and frame of reference. For a natural person, trying to be good according to God’s absolute standard is like a goldfish trying to live outside of his comfy fishbowl home. It ain’t gonna happen.
A silly idea is current that good people do not know what temptation means. This is an obvious lie. Only those who try to resist temptation know how strong it is. … That is why bad people, in one sense, know very little about badness. They have lived a sheltered life by always giving in. We never find out the strength of the evil impulse inside us until we try to fight it: and Christ, because He was the only man who never yielded to temptation, is also the only man who knows to the full what temptation means—the only complete realist.
Resisting temptation is like bodybuilding; you don’t know how badly you were out of shape until you begin working out, but you will never get into shape until you persist through the initial pain. Self-control is part of the fruit of God’s Spirit, but you can’t passively receive it and then go on to actually control your impulses. It’s more of a Holy Spirit motivation to get in spiritual shape.
Only Satan makes things easy for us, because we’re predisposed to sin. It’s God who makes our lives hard, by motivating us to swim against our enemy’s current, which, by the way, will carry us to the falls if we refuse to swim for safety.