"you may say that no temptation is ever overcome until we stop trying to overcome it"

1 Corinthians 10:13 (ESV): "No temptation has overtaken you that is not common to man. God is faithful, and he will not let you be tempted beyond your ability, but with the temptation he will also provide the way of escape, that you may be able to endure it." Note that, as Lewis indicates, it is God who limits the believer's temptations and who provides the way of escape--not the believer himself.