O Lord, we were estranged before from paradise, because of eating from the tree. Therefore, lead us into it again by Thy Cross and by Thy Passion, my Savior and my God. Fortify us therein that we may fulfill our fast with becoming purity, and worship Thy divine Resurrection and Passover of salvation, by the intercessions of Thy Mother.
-- from Orthros, Tone 2
For those observing the Lenten Fast, Cheese-Fare Sunday is the last day on which eggs and dairy are eaten before Pascha.
On Cheese-Fare Sunday, we also commemorate the expulsion of Adam and Eve from Paradise, entering into the Lenten fast in remembrance of mankind's separation from God through disobeying his commandment to fast from the fruit of the tree. Furthermore, many faithful attend Forgiveness Vespers on Sunday evening, asking forgiveness from each other in accordance with the Lord's words: If you forgive men their trespasses, your heavenly Father will forgive you; but if you do not forgive men their trespasses, neither will your heavenly Father forgive you your trespasses (Matt. 6:14).
General Lent Resources
Read more about Cheese-Fare Sunday , in an excerpt from Great Lent by Alexander Schmemann
How and Why Do We Fast?  by Fr. Steven Ritter
A Lenten Reflection: Christ, Our Model for Forgiveness  by Fr. George Morelli
Listen to Fr. Thomas Hopko's reflections on the Forgiveness Sunday on Ancient Faith Radio: