If the sub truly knows you then groveling shouldn't be a factor. You can state Your anguish without having to grovel and if the sub is looking for You to grovel my guess is there is a secondary issues in there somewhere that needs attention. And in some ways... i think groveling, especially at the incorrect times, can have as much of a negative effect on my respect level for someone as if they didn't admitting to the mistake to start with. Guess that would depend a large part on the sincerity of the initial apology and such... otherwise it would be a trust loss issue for me then.
Just me 2 cents worth again....