The brain gets used to you taking the drug. Some drugs will affect your neurotransmitters, or messages that get sent to your brain that regulates how we think or feel. You will eventually become dependent on the drug so if you stop you might feel sick or go through "withdrawal". Which people dont want to go through so they will continue to take the drug.
Narcotics are also called opioid pain relievers. They are only used for pain that is severe and is not helped by other types of painkillers. When used carefully and under a health care provider's direct care, these drugs can be effective at reducing pain.
To seek help with your stress with a parent or counselor