Your question reminds me of a story that I have found illustrative of this matter. There was once a camp meeting with many pastors taking turns preaching. A young pastor took his turn at the pulpit. He preached on the wickedness of sin, with all the pulpit pounding, and voice raising and emotional display he could muster. On finishing he was amazed that the crowd was not moved to answer the invitation. He was followed by an old pastor who talked about what heaven will be like. His words brought the people to the invitation in droves. After he finished, and left the podium, he proceeded taking a plug of tobacco from a pouch in his coat. The young preacher approached him and asked, "What is your secret?" The old preacher, put in the plug of tobacco, waited a moment and then responded, "I reckon that a man preaches about what is in his heart!"
That being said, our choice of content and our most powerful content often reveal what is in our heart.