Bryan Chapell puts it well:-

Application may be attitudinal as well as behavioral. In fact, the frequent mark of immaturity among preachers is too much (or too early) an emphasis on behavior. Mature preachers do not ignore behavior, but they carefully build an attitudinal foundation for whatever actions they say God requires. This is more than a rhetorical tactic. Its source is the biblical insight that out of the heart come the issues of life (Prov. 4:23). Sermons that merely instruct—don’t drink, don’t smoke, don’t lust, don’t procrastinate—will lead to little spiritual maturity, even if parishioners do all they are told. Many applications exhort action (e.g., share the gospel with a neighbor, turn from a sinful practice, give to a worthy cause), but just as many should identify an attitude needing change (e.g., prejudice, pride, or selfishness) or reinforce a faith commitment (e.g., grasping the freedom of forgiveness, taking comfort in the truths of the resurrection, or renewing hope on the basis of God’s sovereignty). Transformation of conduct and heart are both legitimate aims of application.

Christ-centred preaching: redeeming the expository sermon