That is the problem with being persuaded to believe. It's only in the soul, and it may take more than awhile to sink into the heart.
When the Gospel is preached, it should not be directed at the soul, but at the heart (spirit) of man. If a man receives the Gospel in his soul, the heart does not profit from it. The man can join a church, a group of believers, etc., who may "believe" they are saved. Well, to paraphrase the Apostle Paul, "At least they heard about Jesus!" But the soul (flesh) profits nothing, "...it is the Spirit that gives life."
When the Gospel enters the heart, the Holy Spirit begins to dominate the body through the tongue (the soul). Because it is through the heart that man believes God: it is i through the soul that man submits to God, and it is with the body that man obeys God. The body gives evidence of who is winning the battle: the Spirit, or the [fleshly] soul.