I grew up going to church but I’m not religious now and I never really understood this part.
Please, no answers along the lines of “aha, that’s why Christianity is a sham” or “religions aren’t logical”. I don’t want to debate whether it’s right or wrong, I just want to understand the logic and reasoning that Christians use to explain this.
The “be a good person” and “you’ll be forgiven” are two separate ideas. Digging into it requires digging into a lot of different religions and their beliefs. Churches and people disagree on how those go together.
I don’t feel your request of “understanding the reasoning that Christians use” relates well to the question in your title. Much of religion now is repeating dogma rather than spiritual awareness and bettering yourself.