Punishment will usually be something the sub particularly dislikes... and NOT something I particularly enjoy. And as others have said, in whole or in part, the purpose of punishment is to teach a lesson and to permit forgiveness.

So an excellent way to thank me is to request I now take my pleasure... even if it may also entail an activiy you, as the sub, might not particularly enjoy. Asking for that particular activity is, in essence, your gift of thanks.

Of course, if it's an activity you also enjoy... it's all good, but if it's an activity your Dom knows you dislike, it makes the gift, and your contrition, all the more special.