It depends on why he is feeling bad. Is it regret over what he's done to you? Or is it a drop of endorphins. If it's the former its only him that will be able to reconcile his desire to hurt you over his desire to protect you. If it's the latter, then if you are able, get him some water, some electrolytes a banana perhaps.
To help him feel okay with what is done, reassure him that you also enjoy what is done. Most of all, just try and be there for him during his recovery period.