I'm in an Apple store, so I don't have a ton of time to compose this, but here goes:
You can't make much of an impact on the world if you're not happy with your life. You'll spend most of your time trying to find happiness, instead of moving on to help other people be happy.
Now that I don't believe in 'saving' people (in the Christian sense), there isn't a higher purpose for me other than helping others find contentment.
Now that I've found contentment, I can start to focus on others.
Note that me finding happiness or contentment isn't because I've bought things or have cash in the bank.
It's the state of mind that my blog post talks about (and how I'm tempted to break out of it all the time).
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.
You may "believe" in Maslow's hierarchy, but whether it is truth is certainly up for debate. Even the "Criticisms" section on the Wikipedia page you link has plenty of legitimate debate. As with most psychology, it is a soft science at best and pseudoscience at worst.
Through your own missions work, you must have certainly met plenty of people (or at least heard plenty of stories) of people possessing far less on that hierarchy than the average American who were far more content and held an "actualized" attitude about life.
The very highest definition of love (Greek - agape), often denotes self-sacrifice, something that certainly goes against the grain of an ego-driven desire for personal happiness. I'm sure you know it all too well as a parent and the many sacrifices you make for your kids =) I think we live too much of our lives worrying with an inward focus when the real answer is to take that energy and turn our focus outward to others. Self-centered may have been a harsh word, but it is what it is.
I believe contentment goes the other way around. The easiest way to find contentment is to help others. It has been shown that volunteering is a very reliable long-term happiness boost, for example.
It seems to me that most people want contentment and happiness in the same way most people want wealth, which is passively. I think that many of those who decide to be happier can take all proactive action to come closer to the state of mind they desire.
You can't make much of an impact on the world if you're not happy with your life. You'll spend most of your time trying to find happiness, instead of moving on to help other people be happy.
Now that I don't believe in 'saving' people (in the Christian sense), there isn't a higher purpose for me other than helping others find contentment.
Now that I've found contentment, I can start to focus on others.
Note that me finding happiness or contentment isn't because I've bought things or have cash in the bank.
It's the state of mind that my blog post talks about (and how I'm tempted to break out of it all the time).