You are bound to whatever promise you make to God, though our diocese observes the following concerning Lent.
We are encouraged to fast throughout Lent. Everyday but Sunday is a FAST day meaning one big meal and two smaller meals. Liquids are ok throughout the day.
Every Lenten Friday, Ash Wednesday Ember days and Good Friday are also abstinence days (no meat, excepting fish and cold blooded animals). Sundays are free from dietary penance.
The following days are also diocesan feasts and are dispensed from the Fasts- you may also dispense from your Lenten promise depending on the nature of your promise (if you promised “Lord, I will do XYZ for the 40 days of Lent then keep that). These days are: 7th March (St Thomas Aquinas – just past), 17th March (St Patrick), 21st March St Benedict), 24th March (St Gabriel), 25th March (Annunciation), and 3rd April (Our Lady of Good Hope).