Addiction is a way of thinking and behaving that can lead to a person needing a particular thing or activity to feel good. It can be very hard to stop, even when the addiction is causing problems in a person's life. Think of it like a habit - if somebody has a habit of eating candy every day, they don't feel right if they don't eat candy. The same way, someone with an addiction needs more and more of a certain activity or substance to feel okay.