The popular notion of how to deal with the bad things we do (sin) is reflected in the way many people observe Mardi Gras and Lent. Mardi Gras (Fat Tuesday in French, called Pancake Tuesday in England) "is a lively, colorful [not to mention bawdy and debased] celebration held on Shrove Tuesday, the day before Lent begins," says the World Book Encyclopedia. It "goes back to an ancient Roman custom of merrymaking before a period of fast." The idea seems to be to get as much revelry and additional sin out of the way before you decide to do anything about it. But that doesn't show that you think sin is really wrong!
Then comes Lent, a time of "fasting, prayer and self-sacrifice" and "penance." It's not bad to fast and pray, and self-sacrifice is good all year. But it seems the purpose is "penance," not repentance.
Penance is "compensation for an offense" (Merriam-Webster's Collegiate Dictionary), but we can't pay for our sins—only Christ can.
God wants us to repent. "When we repent we must turn away from the sins we are guilty of committing, and we must unconditionally surrender our will to God" (Transforming Your Life: The Process of Conversion, page 17). It's a change in our way of thinking in response to seeing what's so bad about sin and what's so good about God's laws. It's being grateful for the awesome sacrifice that paid for our sins.