Elder Gary E. Stevenson - Nourishing and Bearing Your Testimony

 In teaching us how to continue to nourish and bear our testimonies, he told the story of Elder Matthew Cowley as he went on his mission - 

"...his last words to me at the railroad station, ‘My boy, you will go out on that mission; you will study; you will try to prepare your sermons; and sometimes when you are called upon, you will think you are wonderfully prepared, but when you stand up, your mind will go completely blank.’ I have had that experience more than once.

“I said, ‘What do you do when your mind goes blank?’

“He said, ‘You stand up there and with all the fervor of your soul, you bear witness that Joseph Smith was a prophet of the living God, and thoughts will flood into your mind and words to your mouth … to the heart of everyone who listens.’ And so my mind, being mostly blank during my … mission … , gave me the opportunity to bear testimony to the greatest event in the history of the world since the crucifixion of the Master. Try it sometime, fellows and girls. If you don’t have anything else to say, testify that Joseph Smith was the prophet of God, and the whole history of the Church will flood into your mind.”"

On the matter, quoting the First Presidency - 

"...President Dallin H. Oaks shared, “Some testimonies are better gained on the feet bearing them than on the knees praying for them.”"

"President Henry B. Eyring lovingly taught us that “feasting on the word of God, heartfelt prayer, and obedience to the Lord’s commandments must be applied evenly and continually for your testimony to grow and prosper.”"

"President Dallin H. Oaks reminded us that to retain our testimony, “we need to partake of the sacrament each week (see D&C 59:9) to qualify for the precious promise that we will ‘always have his Spirit to be with [us]..."

"...President Russell M. Nelson kindly counseled recently:

“Feed [your testimony] truth. …

“… Nourish yourself in the words of ancient and modern prophets. Ask the Lord to teach you how to hear Him better. Spend more time in the temple and in family history work.

“… Make your testimony your highest priority.”"

In conclusion - 

"Brothers and sisters, I invite you to seek opportunities to bear your testimony in word and in deed."