While many are familiar with food aspect of "Fat Tuesday," originally it was designed to be a day to confess sins and prepare spiritually for Lent.
A 19th-century writer, in his book The liturgical-class book, briefly explains the history of this day before Ash Wednesday.
The Tuesday after Quinquagesima Sunday that is the day before Ash Wednesday is generally called Shrove Tuesday a name given to it from the old Saxon words, "shrive," "shrift" or "shrove," which signify "to confess;" it being a constant custom amongst the Roman Catholics to confess their sins on this day in order to receive the Blessed Sacrament and thereby qualify themselves for a more religious observance of the holy season of Lent immediately ensuing.
This was the primary practice in the Catholic Church for centuries, until "carnival" took over in popularity. Then it became much more about "feasting" on the last day before the big fast of Lent.
Confession remains an integral part of Lent, as it is a way to break free from the chains of sin and rejoice in the freedom of virtue.
If you are looking for a way to prepare yourself for Lent on the last day before the season, see if a local parish has confession and prepare your heart to receive the many graces of Lent.