Like all the others, Dominican Penitential Practice has to be unique; it has to serve the preaching character. If I was to try and go without food for 24 hours before preaching, I probably would not do very well. As with the rest of the supports, though, the preaching mission will always be more effective if the Dominican friar embraces appropriate penances.
Our Constitutions actually refer to faithful Regular Observance as a penance, saying that we should, “practice the virtue of penance especially by observing faithfully all that belongs to our life.” (LCO 52) The best Dominican Penances, like most aspects of our life, are chosen and practiced communally – in fact, choosing a communal penance that everyone can agree to is a pretty significant penance! Once they’re chosen, and embraced, communal penitential practice edifies both the community and people around the community.