I have a testimony that God answers prayers, and that the process for receiving revelation really works.
I was over halfway through my mission, and I remember my companion and I talking to many different people; two of which I remember vividly. One of them had left the Church and was very lost. The other questioned whether God even existed.
I found myself starting to question many things, but at the forefront of my questions was, "Does God exist?"
I was ashamed that I even had these questions. I was a missionary! I was supposed to be teaching people about God. If I didn't know these things, how was I supposed to teach people who were questioning from a place of sincerity and certainty?
During my personal study one day, I found myself thinking about Joseph Smith and his story. I thought that if Joseph Smith could receive answers to his questions, I could receive answers to my questions, and that ONLY God could answer my question.
So I studied, and prayed every day for him to help me to know that He was real. I studied Elder Holland's "Lord, I believe" talk, and many other talks like it in addition to the scriptures.
Sometimes I got frustrated because I felt like I wasn't getting any answers.
As I look back now, however, I have realized that He was giving me answers all along-little breadcrumbs for me to follow.
A couple weeks later, it was time for General Conference, and I prayed for Heavenly Father to help me find answers. When I heard the first talk, I felt an overwhelming warmth that could have only come from the Spirit. And I KNEW that God was real. I knew that He had answered my prayers.
As missionaries, we go on missions expecting to help others to be converted but I think the most important person you can convert is yourself. I know that God lives, because He has answered my prayers perfectly. He is the ONLY source of truth and light.