From today's Gospel:
"The days will come when the bridegroom is taken away from them, and then they will fast." (Mt 9:15)
Jesus is the Bridegroom of every soul. How do we treat him? Fasting is not about punishing ourselves, but opening ourselves up to the needs of others. Fasting need not be a 30-day marathon on bread and water. Depending upon your circumstances, it can be as simple as eating 1 piece of candy instead of 3, or 1/2 a piece of pie rather than the entire piece. These are little things everyone can do without attracting much notice.
Consider fasting today in some way or abstaining from a favorite activity, and pray that you will always be obedient to God's will.