Empirically, people who succeed on a grand scale work their asses off because they love (or are addicted) to their work.

So no, you won't be as productive if you aren't addicted to your work, don't love it, and/or don't think about it all/most of the time. (aside: yes, you need to eat well and exercise and take a breather from time to time).

That said, productivity/achievement might be a bit overrated. Will your life be better and will you be happier when you achieve your goal? Will you ever achieve it? Most of us disregard the fact that wealth is not remotely correlated with happiness and still hunt for the big payday.

[edit: lots of folks are asking for data. FWIW, I founded and ran RescueTime, so I was hip dip in this world for a long time.

The data actually shows that, for line workers, hours worked have diminishing returns. However, when you look at people at the top of their game (executives, etc), they work extreme hours. Correlation does not equal causation, of course. But when you look at the most successful/productive people in your circles, how many of them talk about work/life balance, have lots of hobbies, etc? Maybe they're successful DESPITE their crazy work hours, for all I know.]