According to the USCCB:
Apart from the prescribed days of fast and abstinence on Ash Wednesday and Good Friday, and the days of abstinence every Friday of Lent, Catholics have traditionally chosen additional penitential practices for the whole Time of Lent. These practices are disciplinary in nature and often more effective if they are continuous, i.e., kept on Sundays as well. That being said, such practices are not regulated by the Church, but by individual conscience.
And canon law:
Can. 1249 The divine law binds all the Christian faithful to do penance each in his or her own way. In order for all to be united among themselves by some common observance of penance, however, penitential days are prescribed on which the Christian faithful devote themselves in a special way to prayer, perform works of piety and charity, and deny themselves by fulfilling their own obligations more faithfully and especially by observing fast and abstinence, according to the norm of the following canons.
The only thing that the Church requires is fast and abstinence on the assigned days. Anything beyond that is up to individuals to decide on their own. Some people might give something up, others might do something extra.