Great post, Gary! I reread The Fountainhead by Ayn Rand this summer in conjunction with my teenage son, and your post could have been co-authored by her. The one additional point she might have made, which I would agree with, is that your happiness can often come from your passion for your work. That work may be purely selfish or it could be that it has a positive impact on other people, but you pursue the work with passion because you love the work itself, not because of what it gets you in the end.
A fitting motto heading into Labor Day weekend!