Jesus was a sacrifice for all time and through Christ you have the foregiveness which you wouldn't have otherwise.
And it is now 2000 years latter, and all Christians can do is claim it's a sacrifice for forgiveness for sins with no tangible evidence besides they feel forgiveness. A "feeling" is the only proof. Nothing else! or as they say you have to be "born again" and share the feeling I feel to know in your heart. Sounds like wishful thinking turned into positive proof from a feeling only they have and nobody else has that doesn't feel the same way.
Not very convincing! A much better explanation in my mind would be that this feeling is generated by a desire indoctrinated in them from religious up bringing or wishful thinking turned fact by repeated indoctrination sessions and uncritical thinking.