I imagine it would depend on what level of achievement one considers a success. The most productive people I personally know (those who average mid six to eight figures per year) work hard AND smart. Of course, none of them are worker drones (they have a fair amount of autonomy in what they do), but they all tend to work 15-18 hours per day 6 to 7 days per week until they either sell their business or finish whatever project they're working on, then wait a while until starting another business or heading another project. This article fits the type of person I'm talking about
: After succeeding, young tycoons try, try again | Tech News on ZDNet
Of course to succeed in much outside of work, I'd emphasize the working smart aspect to reduce the need to work hard, I just wanted to emphasize that the two aren't mutually exclusive of each other.