From Old Testament times, ashes on the head were a sign of deep grief and contrition over sin. (Jeremiah 6:26; Isaiah 58:5; Daniel 9:3, Jonah 3:6--to name a few.) It is a symbol of how sad we are to have sinned against God.
Okay, so what in the world is Lent all about anyway? So you're sorry for your sins. Why do you spend 40 days of "giving up" something, etc.? Let God forgive you and get on with life!
I have addressed the need for Lent in past posts. Briefly, let me just say, Lent is so important in the life of any Christian. It mirrors the time Jesus spent in the desert, prior to His baptism and the beginning of His public ministry. It is a time of "coming apart" with God--fasting, prayer, and alms giving. Before becoming Catholic, we did have times of fasting. And they were powerful times. Lent is a time of Church-wide fasting. Talk about powerful!
I've been asked, too, why we are being "forced" to fast? We aren't! No one is "forced" to "give up" anything. We are encouraged, however, to use this time to set aside things that are peripheral. We are encouraged to use that time or resources, to help draw us closer to God. For instance: Give up TV--spend that time in extra prayer or mediation on Scripture. Give up sweets--give the money you would have spent to help the poor. The main point of Lent: use this time to allow the Holy Spirit to search you:
"Search me, O God, and know my heart; try me, and know my anxieties; and see if there is any wicked way in me, and lead me in the way everlasting."
Psalm 139: 23, 24
One last thing to mention. The ashes are put on people's foreheads in the sign of a cross. This is yet another way we identify with Christ. The sign of His cross emblazoned on our faces for all to see. We should show His death and resurrection in our lives in such a visible way EVERY day. The ashes are a reminder of that!
These 40 days are a time of preparation. Preparation for remembering Christ's temptation in the desert, His baptism, His triumphal entry into Jerusalem, His offering at the Last Supper, His death, and His resurrection. The Feast of Easter becomes so much more real and exciting after 40 days of preparation!
Again, feel free to post questions. May God grant you a blessed Lent!