The Practice of Lent

Dear People of God: The first Christians observed with great devotion the days of our Lord’s passion and resurrection, and it became the custom of the Church to prepare for them by a season of penitence and fasting. ... I invite you, therefore, in the name of the Church, to the observance of a holy Lent, by self-examination and repentance; by prayer, fasting, and self-denial; and by reading and meditating on God’s holy Word. ~BCP 264-5, Ash Wednesday
"What are you giving up for Lent this year?” was a common question when I was a kid. Why would we prepare by fasting?
One traditional reason which we no longer accept is the idea behind asceticism in general: that the body of flesh and its desires are bad and only the higher things of mind and spirituality are valuable or good in the eyes of God. In this view you mortify the flesh in order to subdue its desires and thereby get closer to God. This mind-body dualism comes from Plato and the church fathers rather than from the Jewish tradition in which Jesus was raised. It did get into Christianity very early and we've only fairly recently got rid of it, mostly.
The basic idea of taking time during these 40 days to prepare to receive and celebrate the great blessing of God at Easter, however, is still useful and good. Even fasting and self-denial can have their place when understood not as punishment but as a means to draw our attention toward God. Approached this way the body becomes our ally not our enemy. If you deny yourself something that you ordinarily enjoy for the sake of preparation and spiritual growth, then each time desire arises you can use that as a cue to pray or give thanks instead. Fasting can work in a similar way. When hunger arises and you experience a yearning for food, you can use that as a reminder of your yearning for God and for a world filled with God's justice and peace.
Self-examination is also very helpful but we want to get beyond the traditional implication of self-judgment. St. Ignatius, who created the Ignatian exercises—one of the earliest organized systems for spiritual growth in the Christian tradition—taught a daily practice called the examination of consciousness, often referred to simply as the examen. You can do it in your head, but it's even better to write it in a journal so that you can look back from time to time and see where you've been. In doing the examen you basically ask three questions—two of yourself and one of God.
You ask yourself, “In what ways have I been blessed today? Or, “What am I thankful for?” Make a list. At least three items. Challenge yourself not to use the same three things all the time but to expand your appreciation. Give thanks to God. Then you ask, “Did I do anything harmful, for which I need forgiveness?” and “Is there anything I'm struggling with, where I want God's help?” Finally you ask God directly for forgiveness and help with these things.
This deceptively simple exercise has transformed many people down through the years, bringing them to a place of greater hope and joy in God.