I see many of the most famous, successful people in business, politics, law, entertainment, education, and other fields have been arrested, done drugs, or both. In fact, I'm having trouble thinking of highly successful people who have never been in either category.

How are you going to take the necessary business risks to be the next Bill Gates or Richard Branson or Steve Jobs (or U.S. President or genre-creating musician or ...), if you can't take a small personal risk? There may be a benefit to "staying clean", but it appears to be dwarfed by the ability to take calculated risks.

If you want to abstain for the sake of abstention and staying out of jail, then by all means do so. But if you think smoking cannabis is going to sink your career when you start becoming successful, I see no indication of that.