It is freeing as an agnostic atheist; I've dropped the idea of sin. An unproven being cannot be 'sinned' against. The bible to begin with was written by man, until God himself visits all of humanity to introduce themselves...The shackles of sin that Christians wear is for them alone. No amount of shame or anger those believers attempt to burden me with will cause me to adopt the concept of sin again! Their creator must prove that it exists, as the burden of proof always lies with the one who presents an idea.
I simply act with a moral compass that guides me into not doing illegal or shitty things to other human beings. I feel this is enough to live a good life.