Living a life without god is a conscious choice. You learn about the religions of the world and if nothing appeals to you, decision is made to do without it. You don't judge those who do believe and you can only ask of them to do the same for you. As you get older and you experience more you start questioning your decisions. Did you get it all wrong? Maybe there is a god and he is punishing you for abandoning him. Do your skeptic thoughts mean that maybe you do believe in more than you want to acknowledge?
You look at those who have faith with envious eyes and you wish you could find it within you to believe as strongly as they do. Their faith gives them answers you so desperately seek and for a brief moment you consider converting.
You then realize you can't make up faith not matter how strongly you want it. It's wrong to disown something when things are going well and come crawling back when things are bad. Either you believe or you don't. Something else needs to fill the emptiness inside and that becomes your quest. Who provides you the answers?