From the Ash Wednesday liturgy:
"Even now, says the Lord, return to me with your whole heart, with fasting, and weeping, and mourning; Rend your hearts, not your garments, and return to the Lord, your God. For gracious and merciful is he, slow to anger, rich in kindness, and relenting in punishment."
The phrase, "Rend your hearts, not your garments," has always struck me with its succint poetry. Sacrifice and mortification are worthwhile, but not for their own sake. My Lenten observances should not be cultural or on the level of New Year's self-improvement.
God wants me to fast for love of Him and sorrow for my sins. That's my challenge this year--to not just keep my commitments, but to keep the reasons in mind.