Edmund Clowney once asked Martyn Lloyd-Jones how he might know if he was preaching in the Power of the Spirit. What a response from Lloyd-Jones:

“On one occasion I had tea with Martyn Lloyd-Jones in London, and decided to ask him a question that concerned me. “Dr Lloyd-Jones,” I asked, “How can I tell whether I am preaching in the energy of the flesh or in the power of the Spirit?”

That is very easy,” Lloyd-Jones replied, as I shrivelled. “If you are preaching in the energy of the flesh, you will feel exalted and lifted up. If you are preaching in the power of the Spirit, you will feel awe and humility.”

From Preaching Christ in all of Scripture, pg 55