I decided that I wanted to go to church when I was 25, and I encountered years of wishy-washy, liberal, "believe what you like - it's all good" types of believers. Eventually it drove me to atheism, something for which (ironically) I thank God. After 11 years of atheism, arguing with Christians on forums and generally being a non-believer, everything changed in a car journey from London to Bristol. I instantly believed.
I was so blown away by the experience that it emptied my mind of all considerations that I chose God. It was clear that God had chosen me.
I've pursued discussions along the lines of self-deception, wishful thinking, guilt-driven conversion and the like. I don't buy it. My studies led me to examine a theology where God acts on Man and guess where I ended up?
My final conversion was about 3 years ago. In that time, my atheist son and his atheist wife have both become Reformed Christians, and church is the only place where my 5 month old grandson Caleb will sit for an hour and a half without a murmur. Only God can do that...
So I try to thank god every day, rather than giving myself the credit for being good enough to choose Him. It makes more sense that way.