How would you describe that burning emotion of having messed up? It's a mix of guilt and being deeply unsettled, together with crushing embarrassment.
-When he realized he had given his wife AIDS, he was overcome by deep [word].
-She checked her account balance and realized with [word] that she had underestimated how expensive the mortgage really was.
-After becoming a cuckold, he realized With [word] that he couldn't call himself a real man anymore.