You can't make much of an impact on the world if you're not happy with your life.This sort of self-centered attitude (i.e. "my own happiness must come before others") is the same line of reasoning that people use to say "you can't love others before you love yourself", but it's just not true.
Happiness often comes when we consciously decide to take the focus off ourselves (and all the moaning and worrying we do about our "unhappiness") and place it squarely on the well-being and loving service of others. It's a daily choice to lose ourselves in something far greater than our ego and its want of fickle satisfaction.
Now that I've found contentment, I can start to focus on others.
I'm not going to judge your motives, but I would question if you've really found true contentment -- you're living an extremely favorable set of circumstances in life (a great wife, kids, a fantastic business) that make it easy to be happy -- and yet here you are, writing a blog post about how it's still not enough. The business has to be bigger (more barns to build!), you want more money than 99.9999% of the world to retire early, etc. You know your own heart though.
I struggle with the same thing too on a monthly basis, the constant pull towards discontentment. I often find it's when I've stopped giving thanks daily and, consciously or otherwise, allowed myself to believe that "these material things matter and they are mine to have".
With that said, I would say true contentment is really understanding Job 1:21 and the perspective that brings.