For instance, after taking heroin you just feel sleepy. When you first start taking it you don't feel anything bad, so you think there's nothing wrong with taking drugs, but in fact you're already hooked.
吸毒時的感覺，也不像傳說的「會飄飄欲仙」，像海洛英吃了頂多是想睡覺；剛開始吸毒時沒感覺，才剛覺得吸毒沒什麼，其實已經上癮了。