Hi Dawn.
My individual justification for letting go of God began with recognizing how well people can delude themselves, including myself. I got on a kick of looking into commonly held myths - things that most people think are true, but aren't. You know, stuff like "Shaving makes hair grow faster.", and "The moon is magnified by the atmosphere when it's low on the horizon."
Then I looked into things like OBEs and NDEs too, that seem to support the existence of a soul. I found no trace of it, but learned a lot about the trickiness of human mind. This led me to James Randi, Michael Shermer, and the skeptic crowd; and the amazing variety of delusions that humans are capable of embracing.
I got it into my head that I could understand the world better, and live a more honest and less confusing life, if I didn't accept anything as true unless I had very good reason to, and I also faced the fact that truth is rarely black and white except when it's perceived by a human mind.
Like the Creationists' God of the gaps, my god was always being chased into the narrowing cracks of my understanding of the world and the human condition. Ultimately, He became just some vague cosmic guy in the sky who (maybe) lit the fuse for the (maybe) big bang.
From there it was a small step to saying "Goodbye".
™ Version 4.2