My experience is that "where sin abounds" condemnation abounds. If I screw up in the slightest, I get an immediate bullet to the head. Maybe grace is for other people, but not for me. What am I missing?

Maybe your meaning of grace is connected with how you think others should treat you rather than how you truly exist as a new creation in Christ. I'm not suggesting that Christ in another shouldn't or won't affect how the other views you and therefore treats you, but I suspect that what you say and perceive about grace is only connected with how you think you haven't been treated in grace by those who give you the immediate bullet to the head. You must know this grace between yourself and God first and foremost. I hear your confidence waiting to be established upon how someone else views and treats you and not upon Christ alone.

Jim