there are certainly people who are successful and use drugs at the same time. There are much more people who don't have that success and whose life's are pretty sad.
I am from the Netherlands. We have a regulated market. I totally support our system. But the system is not there to promote the use of it. It's to prevent criminal organisations selling to youth. It ensures a certain level of quality and service.
Marijuana does not make you sharp. That's an illusion. Enough studies confirming this.