The only rules that apply to your life are the ones you make or accept. So you are absolutely free to live your life as if the only thing that matters is success in your ventures or projects. You may think that since you are young, you will have plenty of time later (especially once you are independently wealthy) to live a more fruitful, meaningful life. That is a common misconception.
Just like you are learning to work better, you also have to learn to live better. You have to grow yourself at the same time as growing your business. Or else at age 35, you will be no different than a rich 15 year old who has 20 fewer years to enjoy life than everyone else.
Depending on your goals, hobbies, and capabilities, you can do a lot in your life in addition to your work starting right now. I cofounded two decently successful startups in last couple of years, am going to B-school like the article's author, and last week I finished building an aviary/animal-house in my backyard with my wife (for the curious, pics of the structure + animals here: http://chir.ag/gallery/aviary2009 ). Right now, I'm training for an ultramarathon and also working on a neat (and near-and-dear) side-project for a family member.
I'm not saying I'm awesome or better than anyone. I'm saying I could be single-mindedly pursuing one goal and instead, I've decided to pursue multiple goals at the same time, each with different levels of ambition and effort. Many of the goals are work/business related and many are not. There is no doubt that if I work on my projects 18 hours a day, I will get more accomplished in the short-term. But I have learnt over time that living a full, well-balanced life gives me a lot more value compared to the efforts I put in.
While there are a lot of successful people who dedicated their entire lives to one single goal, this doesn't mean if you try to widen your interests you won't be successful in anything. E.g. Ted Turner is a world-class sailing champ: http://en.wikipedia.org/wiki/Ted_Turner#Sailing
I try to model my life after Feynman, in the sense that, I will try to be very good in one or two things, and try everything else with light-hearted but passionate efforts: http://en.wikipedia.org/wiki/Richard_Feynman#Personal_life
I feel that being a http://en.wikipedia.org/wiki/Polymath maximizes the utility I derive from life. I don't think this is the only way to go for everyone, but I do think the sweet spot for most lies somewhere in between single-minded dedication and being a Polymath.