A Christian is someone who is called by God, and then cooperates with Him. That's the order: the divine calling, then the cooperation. The Bible says, "We love Him because He first loved us" (1 John 4:19). We have a responsibility to respond, but it is always a response. God moves, God loves, and we respond.
Often, Christians will try to produce a sense of conviction in unbelievers, to convince them that they're sinful. In and of yourself, you can't produce a conviction that is sufficient to draw a person to Jesus Christ. Only God the Holy Spirit can do that.
In fact, if you were to look back over your life, you would see that it was all a set-up, that the Holy Spirit was leading you, through different experiences and different people, to faith in Christ.
At my school, we had an exchange student from France who was an agnostic. But he gave his life to Jesus Christ one day, and he went around sharing the gospel with people. I saw his changed life, and that was the first little catalyst. Then a band came to school and played Christian music, and that was more conviction in my heart. Then a friend of mine came to Christ and told me I needed to do the same. I basically ran away from him and all my Christian friends, and went to northern California. A couple of them followed me and kept talking to me.
Then finally one afternoon when I turned on the television, there was Billy Graham saying, "You come!" And I accepted Jesus Christ as my Lord and Savior. But a number of things led up to that, as the Holy Spirit was setting me up.
My father-in-law received Jesus Christ after many years of being an agnostic by reading the New Testament. What convinced him wasn't any clever arguments posed to him; it was just reading an edition of the New Testament with the words of Jesus Christ in red. God's Holy Spirit nudged him, and he was convinced that he needed Christ.
The Holy Spirit nudges a person, and convinces a person, and even chases a person. He's been called the "hound of heaven!" Jesus said, "And when He has come, He will convict the world of sin" (John 16:8). Why? "Because they do not believe in Me" (v. 9). The greatest sin is not believing in Jesus Christ, and that's what the Holy Spirit convicts a person of.
Think of the crowds that Jesus spoke to around Galilee. Did every one of them respond by believing He was the Son of God? No. Some did, some didn't. Some walked away. Some were hostile. They heard the same message; what made the difference? The condition of the heart! To hear is different than to say yes and respond.
That's why you should thank God for the people He has placed in your life, and for what you've read or heard, that brought you to the place of salvation. And that's why you should be ready to proclaim Jesus Christ. You never know when someone might be ready to respond!