Drugs and Alcohol
Drugs and alcohol are very bad for teenagers especially because hormone levels are naturally highly irregular between ages 12-23. The drugs and alcohol make those already imbalanced hormones get even crazier. They kill brain cells, inhibit brain function, reduce overall mobility, and can easily lead to addiction that can derail your life. Watch for yourself.
If you are addicted to drugs or alcohol, there is hope. Recovery will be a daily process, but there are organizations available to help.