If you don’t believe the gospel, then you can 1) pretend you are righteous, which you are not. Or 2) you can pretend God does not exist, because the idea of atoning for your own sin is too horrible, or 3) you can self-condemn and beat yourself up as a way of self-atonement.
What are you doing in your relationship with God? Are you beating yourself up, or are you enjoying his grace? Me? I’m going to revel in God’s grace.