I grew up voluntarily participating in protestant religion-I was a "true believer". Of course, it started when I was a very young child, so what I thought of as "true belief" previously I now consider more closely akin to brainwashing...
The beginning of the end was in my mid to late teens, though I didn't realize it then. I was still VERY active in my church, and passionately believed there was a (mostly) benevolent god. The trouble is, I am an extremely logical person, and the assertions of Christianity on practically EVERYTHING seemed painfully illogical to me. Not only that, but I have always been one to consider all sides of any argument/situation, and injustice in any fashion feels like a very real personal injury. I questioned and questioned, I never received even ONE answer that would satisty my need for logic and fairness. By my early to mid-twenties, church (but not God) having been left behind for several years, I realized that I couldn't worship such a deity as the Christians do. I WOULDN'T. It offended my nature to be worshipful of a being so unjust, so contradictory, so f'n MEAN. My sense of fairness made me stop worshiping, but my logic-causing me to continuously question the likelihood of existance of first the Christian God and then ANY such being, ah-my logic killed any deity that existed within my own mind. Which is of course the only place it ever existed at all.
I think the biggest reason I struggled for so long with my disbelief was the fear of HELL I had been continuously reminded of all my life. When I first accepted/realized/decided that I had no real belief in any deity, every time I would consciously think or verbalize that there was no god I would immediately think, "Oh! I am going to HELL!"...before logic once again saved me from such thoughts.
I am happy to have escaped the bonds of Christian brainwashing, yet for a long time I missed my faith. I missed the comfort of "maybe if I pray enough, God will take care of this for me/protect my (loved one)/etc" ... I am infinitely stronger as a person, as a WOMAN (Christianity not being female-friendly) and as a parent. Being an atheist with no parents, no family to speak of (except for my son of course) may have made me feel very alone when I first understood exactly what I did and did NOT believe, but as I've grown into it, it has also made me extremely self-reliant and empowered. My self esteem, once non-existent as a young Christian, now needs a leash with a choke collar--but hey-- I'm AWESOME!