Dan Naulty pens an article detailing his use of PEDs during his professional career, and the harm it caused him. I found this section on positive reinforcement most interesting:

I will say there was not a negative aspect of taking these drugs until later on. As I took them, literally from the second week forward, I don't think I ever got a negative remark from anybody. It was always, "Wow, you're throwing well, you look great." The positive reinforcements of it went well beyond the baseball field. And it was working. I was getting people out. It wasn't just that I was this big, muscular guy. I was also pitching well, which fueled the fire of my addiction. The more people patted me on the back, the more crap I loaded in the needle.

Naulty sits in stark contrast to Jose Canseco. You get the feeling reading his confession that PED use caused Dan to feel guilty from the start. I never got the feeling that Canseco feels any remorse for his abuse of drugs.