“Father, what is meant by the phrase, ‘observing the Friday penance’?”
Good question! In 1966, the Catholic bishops of the United States said, “far from downgrading the traditional penitential observance of Friday, and motivated precisely by the desire to give the spirit of penance greater vitality, especially on Fridays, the day that Jesus died, [we] urge our Catholic people henceforth to be guided by the following norms”. They then established that, “Friday itself remains a special day of penitential observance throughout the year, a time when those who seek perfection will be mindful of their personal sins and the sins of mankind which they are called upon to help expiate in union with Christ Crucified. Friday should be in each week something of what Lent is in the entire year. For this reason we urge all to prepare for that weekly Easter that comes with each Sunday by freely making of every Friday a day of self-denial and mortification in prayerful remembrance of the passion of Jesus Christ.” The bishops also noted, “we give first place to abstinence from flesh meat. We do so in the hope that the Catholic community will ordinarily continue to abstain from meat by free choice as formerly we did in obedience to Church law”.
So, the Passion of Christ+individual freedom=the Friday penance.