I love how Mycroft’s real softer self is shown in this episode. He always had it but never showed. I always liked him but after this episode I love him all the more.
He knows Sherlock can’t even imagine hurting John, let alone killing him, so he tries to sacrifice himself instead. He cares so much about his little brother like he always did. Always protecting him. But Sherlock cares about him just as much. I guess in that moment, Mycroft forgot Sherlock would neverhurt him either no matter what. Not even in his dreams.