"My personal brand of Heroin"

I had my seasonal flu shot yesterday. One of this "intramural" or "intradermal" thing, the one where the medicine is injected between the muscle, the one where the shot site is red and blotchy and slightly itchy for a few days till the swelling goes down. Now, I know better than to scratch. But if my forearm were to 'accidentally' hit something or somewhere then that's relief. You know!! At first its a casual bump here and there and then after a while it doesn't seem so random any more!!

I kinda get why people do drugs!

Can you draw that parallel between them??