Every year around Ash Wednesday, I see and hear comments to the effect of, "Why do Catholics give up things for Lent? Shouldn't you be bettering yourself for the Lord year round?"
Yes, absolutely! Every day we should be striving to be a better Christian, to know God better, and to better give of ourselves to help others. Every day.
For Christians who do not follow the liturgical calendar, I imagine Lent often appears as a shallow, self-centered time. They hear people discussing what they are giving up and the connections to Christ aren't obvious. Is your friend giving up sweets to lose weight or to become closer to God? What does drinking (or not drinking) soda have anything to do with Christ? Unfortunately, many Catholics (and I only speak for Catholics, because I'm one) are poorly catechized and so Lent does become a show of their own self-control or a chance to re-do failed New Year's resolutions, this time with a little extra motivation in the form of Jesus. Rarely do we say, "I'm giving up X because it will bring me closer to Christ and help me share in his suffering. Let me tell you how..."
For those Christians that observe Lent and the liturgical year*, Lent is not the only time to better ourselves. It's not the only time to give up sinful habits. And in fact, Lent is not simply about "giving something up". It is a time of repentance, during which we acknowledge our sinfulness as we approach the yearly commemoration of the Lord's Death and Resurrection and in acknowledging our sinfulness, we cannot help but repent. We strive to understand the sacrifice of Jesus Christ by making sacrifices of our own.
One of the ways we can sacrifice is by giving things up - they need not be sinful things - but things that we will miss and in their absence we will be called to become closer to Christ. For example, someone may give up social media which is not in and of itself sinful (though it can certainly be used that way). In giving up social media, the person will have more time to do more productive Christ-centered things - pray, volunteer, better care for her family, etc. If someone does give up something sinful, it shouldn't be with the intent to take it back up at the end of the 40 days, but in hopes that a long period of time away from that sin will release the hold it has on the person. 40 days is more than enough time to rid oneself of a bad habit...
Or start a new one. Many people choose to add something beneficial in addition to or instead of giving something up: additional prayer time, weekly time in adoration, daily Mass, more quality time with family, spiritual reading, etc.
(For a really great Q&A on Lent, including why we fast, why we abstain from meat, why it's 40 days, why Sunday is not counted, etc. click here.)
So, back to the original question: Why don't we simply better ourselves year round for God? Why do we need liturgical season?
I'm sure there are some fancy theological explanations out there, but I'm not a theologian and I doubt you came to my blog so that you could see me re-quote them. So here is my explanation, a simple lay person's explanation:
We need liturgical seasons because we are human. We are fallible and sinful and limited. Our relationship with God is complex and we are incapable of delving into each aspect of our relationship with him deeply on any given day, or even on our own. The Church knows that we need help. She reminds us at different times of the year to concentrate on different aspects of our relationship with Christ.
Most Christians celebrate Christmas and Easter. Why is that? It is instrumental that we have a special day (or season) set aside to commemorate these important moments in our faith. But shouldn't we be celebrating the message of Christmas and Easter each day? Yes! But we need MORE. It's not enough to leave it to our own devices. We are human. We need help. We need reminders. We need periods of time set aside when we are told, "You need to remember your sinfulness. You need to repent. You need to further your humility," or "You need to rejoice that Christ has saved you by His sacrifice!" The liturgical seasons are not there to put additional limitations and rules on humanity but are there because we as humans are limited. The Church does not demand structure, instead it is the Church who, in Her infinite wisdom, takes pity on our weakness and gives us structure to help us overcome it. The liturgical calendar is a gift!
And if I haven't already gotten my point across, let me share with you a story: Imagine a son and mother. The son adores his mother. Every day, he shows his mother love by obeying her. At bedtime, he kisses her and tell her he loves her. He cherishes his mother. But on a few days a year, he goes above and beyond. A few days before Mother's Day he makes her a card. As he contemplates what to write in the card, he thinks of all his mother does for him and in doing so he becomes even more grateful for her love and sacrifices. He comes to understand more deeply the woman who is his mother and he commits to being an even better son in return. On the days leading up to her birthday, he again prepares a gift for his mother and in doing so, he again begins to reflect on what a gift his mother is, but this time, it being her birthday and not Mother's Day, he reflects on not just her role as his mother but the many roles she holds - wife, daughter, sister, aunt, friend, employee, church member, neighbor, etc - and he is again humbled with gratitute, but this time in a different way, for his woman who is his mother.
We are like that son, we may strive to obey and love our God everyday, but it is helpful to us, in our frail humanity, to live our lives by a calendar that yearly calls us to contemplate Christ in different ways at various times. Lent is one of those times. One of those gifts. Take advantage of it.
*Catholic and Orthodox Christians are not the only denominations that observe the liturgical year. Anglicans, Lutherans, and others do as well.