Read 1 Timothy 4:12, "Let no one look down on your youthfulness, but rather in speech, conduct, love, faith, and purity, show yourself an example of those who believe."
One of the main excuses I get from teenagers when they are challenged for the way they are living is, "I'll do it when I'm older." Teenagers say they will read the Bible when they're older, they'll get serious about their faith when they're older, they'll share the gospel when they're older, they'll go on mission trips when they're older, etc, etc... Have you heard (or used) these excuses before to justify your spiritual laziness or complacency?
The problem that many of us face is that we see ourselves as immortal. No matter how many times we may hear Kris Allen's single, "Live like you're dying," we simply don't go around with the idea that each moment could be our last. Psalm 144:4 says, "Man is like a breath; his days are like a fleeting shadow." Whether we want to face it or not, our lives are short. 2 things could happen at any moment that would cut off your time from this earth. First, I know it sounds morbid, but you could die at any moment. Death happens all around us all the time, even to healthy teenagers like yourselves. This is reality. Second, Christ could return at any moment. We don't know when the Second Coming will take place, but we do know that we are living in the end times, and "the day of the Lord will come like a thief in the night" (1 Thess 5:2).
Do you see the flaw in the reasoning of those young people who are waiting until they're older to really live for Christ? Don't fall into this trap! Instead, take to heart the words of the apostle Paul in 1 Timothy 4:12, given to his young protege, Timothy, "Let no one look down on your youthfulness, but rather in speech, conduct, love, faith and purity, show yourself an example of those who believe." Young believers are not excused from Christian service because of their age! Instead, Paul encourages Timothy to serve God in His youthfulness, setting an example of Christian living to others, despite his age.
Notice the 5 different areas of Christian living that Paul mentions to Timothy in this verse. First, Paul mentions his speech. I'm sure you are fully aware that young people have a problem with filthy speech! Though there are many adults who also struggle with this sin, I think cussing and coarse jesting may be the worst in young people. For example, if you heard a teenager use the "f" word, you probably wouldn't bat an eye, but what if you heard a middle-aged woman or an elderly man use the word? That's a lot more alarming! Young people who have tamed their tongue will really shine in their generation. If you vow not to use your tongue for cussing, filthy humor, gossip, and critical words that tear others down, you will serve as an amazing example to those around you.
Second, Paul mentions Timothy's conduct. Many young people are impulsive and foolish, doing things that older people wouldn't imagine doing. Young people are more likely to do things like hit someone's mailbox or spray graffiti on the wall than older people are. Don't buy into the lie that doing foolish things as a teenager somehow excuses your behavior. You know better. In your youthfulness, live a life that would make Jesus proud. As Matthew 5:16 says, "In the same way, let your light shine before men, that they may see your good deeds and praise your Father in heaven."
Third, Paul challenges Timothy to live a life of love. I'm sure you remember that loving God and loving others are the greatest commandments (Matt 22:37-39). How many people do you see in your schools who are living out these commandments? Not very many, I'm sure! There is so much hatefulness, bitterness, back-biting, and criticism going on today. How radically different you would look if you rose above that and loved people like Jesus did?
Timothy is also challenged to live an example of faith. As people grow older, they generally become more hard-hearted and more skeptical. Studies show that individuals are so much more likely to become Christians before the age of 18 than in adulthood. Hold fast to your faith in Christ despite the different circumstances you may encounter in life. As Hebrews 10:23 says, "Let us hold unswervingly to the hope we profess, for He who promised is faithful."
Lastly, Paul mentions purity. In an age where girls are maturing and losing their virginity at shockingly early ages, take a firm stand for abstinence. However, don't make it your goal to simply keep your virginity, but make purity your goal. This involves keeping your mind innocent of evil, and guarding what you allow into your heart. Are the TV shows, movies, books, and topics of conversation that you allow into your mind and heart pure or impure? Purity is a beautiful virtue for a young Christian girl to display. It not only pleases God, but it provides a powerful witness of your Christian faith to others.
After reading this, do you still believe that you're too young to make a difference? God's plan for you doesn't start after high school or in adulthood. God wants to use you right now, in the place that you are in right at this moment. It is not an accident that you're in your particular community, neighborhood, or school. God has you there for a reason, and He wants to use you for His glory as a young person. Why not embrace this calling and shine for Him in a dark world, just as Timothy did all those years ago??