Our testimonies are ever-changing. If we are not growing them by bringing constant light into our lives, they will slowly diminish. Sometimes despite our best efforts to grow our testimonies we still come across materials, feelings, or others who will make us question our testimonies.
In the words of Elder Anderson,
"Why does the Lord allow the evil speaking to chase after the good? One reason is that opposition against the things of God sends seekers of truth to their knees for answers."
REFERENCED IN PEP TALK:
Joseph Smith- by Elder Anderson
Come, Join with Us- by President Dieter F Uchtdorf
Receiving a Testimony of Truth & Light- by President Dieter F Uchtdorf