It releases serotonin stored in your body, and thus depletes those stores. So multiple doses feel less and less good. The body needs several weeks/months to refill those serotonin storages. All you do is risk getting serotonin syndrome [1] which is a whole other story/problem. But becoming "addicted" (physically or psychologically) in the classical sense is not an immediate issue as it is with cocaine, smoking, weed, etc.