Sometimes, if not all the time, we all get attacked in some way or degree by a non-believer about why do we still believe in a theist concept, why do we believe in just one God, and not more, or why do we still believe, of all things, Christianity. Sometimes it's a total stranger. Sometimes that person is in our family. Sometimes it's a loved one. Sometimes we even doubt ourselves.
I am not here to give you a formula into why we believe in Christianity. That is up to you and God. Christianity is a relationship, not a religion. If it was a religion, then you would just "know" God. Since it's a relationship, you should thenlove God. You know you love someone and that that person loves you too when you talk to them often.
I was raised in a Christian home. I went to church since I was a newborn baby. I was baptized when I was 14 years old. I've been active at church tirelessly. Still there was a time in my life when I had my doubts. It's okay to have doubts, but it's lethal when it festers. I let mine fester. I never doubted God's existence, but I was distant to God. He was in the background of my life. But you never know how much you need the Sun until it's nighttime. I felt one day the need to declare what I believed. Nobody asked me. I just had to find a way to stand my ground when I asked. I came up with a silly argument that when I made a closer examination, I was contradicting myself, so I kept on and on till I was making myself confused. I noticed that my argument proved solid every time I used a Christian truth. It happened again and again till I ended up being a Christian once again.
Now, you may argue that I returned to Christ because I was raised in a Christian home. I may have inherit my parents looks or talents, but I didn't inherit Christianity, in the same way you don't inherit a doctorate. I don't believe in Christianity because my home was a Christian home, but because I believe Jesus is my one and only Savior. He is all I need. I love Him because He loves me more. We all want to be with Him when we die. He wanted to be with us since before the beginning of Time. I will never deny the fact that I've made my share of sins, but I'll never deny that He loved me first and forgave me. Religion tries to please you with favors and sweets. Christianity feeds you with flesh and blood. "EAT me". "DRINK me".
As I said before, You never know how much you need the Sun until it's nighttime. When you see a light in the middle of a dark room, you don't just watch it. You follow it, you let it guide you. Some of us have been living in the shadows our whole lives, and that's why we need to be the Light of the world, not because they may see God through us, but because we can show them the way to God, which is Jesus Christ.