It is in the context of secret prayer that the eternal verities to which we give constant mental assent become living realities. I find, and this is somewhat of a confession as well as an exhortation, that my own words mock me too often when I preach — when I can say the word ‘hell’ and not feel the horror of it; when I can speak of heaven and not be warmed with a holy glow in the light of the fact that this is the place my Lord is preparing for me. I find no answer to this problem but to meditate long upon the passages that speak of these spiritual realities, and ask God the Holy Ghost to burn them into my heart. I plead with Him to make real to me that the very people that I look at may hear those terrible words, ‘Depart from me, ye cursed, into everlasting fire.’ I find I must plead with God to make real to me that the people whose voices will say to me at the door, ‘Thank you for the sermon, pastor’, are the very voices that may one day be uttering those cries and groans of the damned. I must ask God to help me to believe these things, to help me to preach them so that others will know that I verily believe them. The truth that burned on Sunday can be icy cold by Monday. The truth that burned in the closet on Saturday can be lifeless on Sunday. Truths received in the crucible of waiting upon God can only be maintained in their warmth in that same context.
(Source: What is wrong with preaching today?)