@KeepHopeful your post is entirely predicated on someone accepting the concept of sin. I don't. I accept that I do my best and that I am fallible. That can't be changed by a deity, because there is none. All I can do is try to do less harm than good and leave the world a better place than I found it in whatever ways I have available to me. And when I do harm, it is up to me to acknowledge that and make reparations.
You keep quoting the Bible as the source of all the answers; again, that cuts no ice with atheists. To us, it's a book of fiction that has been used to do great harm in the world. We want no part of it, nor of any of its counterparts in Judaism, Islam or any other faith.
As forf the research on faith and happiness, I'm sure that holds water on a population level. That does not however mean that it is impossible for a particular atheist individual to be happier than the religious individual standing next to them. I do not see how having a faith would add anything to my life or my happiness.