From personal experience, I was always a big supporter of balance in life (in theory) but I hadn't quite figured out the most optimal career/life balance (until now). In past years, I would cycle drastically between my two passions, sometimes working 90 hour weeks at Silicon Valley startup companies and then running from high-tech burnout to training for Ironman triathlons.
This was one difficult way to learn how important balance can be to a happy and healthy lifestyle. Making exercise part of your lifestyle requires it to be integrated seamlessly into the rest of your daily commitments. Training right and eating healthy will reduce stress and give you more energy. Make a simple goal. Make it a priority to feel better and you'll actually find that you have more quality time to get things done.