Many teens give in to what is called peer pressure. They want to fit in a group, sorta like a gang, and they are willing to do the stuff that the group does to fit in. This could include: smoking, drinking, vandalism, theft, etc. There are many stories out there of good, honest teens who had great expectations and a great future ahead of them, only to be ruined because they hung out with friends who don't have the same standards.
Elder Malcolm S. Jeppsen talked about doing medical check-ups and said this: "Some years ago in my medical office I had occasion to examine a young man approximately the same age as you young men of the Aaronic Priesthood. After several tests, I found myself amazed. He was an alcoholic! He told me he had begun having alcoholic drinks at a very early age due to the encouragement of his so-called “friends.""
Sometimes, people are in a lot of pressure, from both friends, and from teachers/coaches. Here is a story about a young man who chose the right.
When he was 16 years old, Brother Christensen decided, among other things, that he would not play sports on Sunday. Years later, when he attended Oxford University in England, he played center on the basketball team. That year they had an undefeated season and went through to the British equivalent of what in the United States would be the NCAA basketball tournament.
They won their games fairly easily in the tournament, making it to the final four. It was then that Brother Christensen looked at the schedule and, to his absolute horror, saw that the final basketball game was scheduled to be played on a Sunday. He and the team had worked so hard to get where they were, and he was the starting center. He went to his coach with his dilemma. His coach was unsympathetic and told Brother Christensen he expected him to play in the game.
Prior to the final game, however, there was a semifinal game. Unfortunately, the backup center dislocated his shoulder, which increased the pressure on Brother Christensen to play in the final game. He went to his hotel room. He knelt down. He asked his Heavenly Father if it would be all right, just this once, if he played that game on Sunday. He said that before he had finished praying, he received the answer: “Clayton, what are you even asking me for? You know the answer.”
He went to his coach, telling him how sorry he was that he wouldn’t be playing in the final game. Then he went to the Sunday meetings in the local ward while his team played without him. He prayed mightily for their success. They did win.
I believe that everyone should choose their friends wisely, and to be strong and not break under peer pressure.