It takes a lot of purification and sanctification before there is no more room in your soul for even the entertainment of a sinful thought. This is the state of God for he cannot look upon sin with the least degree of allowance (Alma 45:16). This is the degree of godliness we must strive for while on the earth. It is a state reached by few.
Immediately after their conversion, king Lamoni and his servants had a change of heart so dramatic that they had no more desire to do evil (Alma 19:33). Jacob had developed this as a permanent quality. The qualities of godliness and purity exemplified by this phrase are difficult to master. We are not likely to be successful in this endeavor without divine help.
“The Holy Ghost is a sanctifier….One who lives worthy of the guidance and cleansing influence of the Spirit will, in process of time, become sanctified. Sanctification is the process whereby one comes to hate the worldliness he once loved and love the holiness and righteousness he once hated. To be sanctified is not only to be free from sin but also to be free from the effects of sin, free from sinfulness itself, the very desire to sin. One who is sanctified comes to look upon sin with abhorrence (cf .Mosiah 5:2; Alma 13:12; Alma 19:33).” (McConkie and Millet, Doctrinal Commentary on the Book of Mormon, vol. 1, p. 263)