Happiness comes from the overcoming of not unknowable obstacles toward a known goal. It's the journey, not the destination. And the trick is to set another goal once you attained the one you're on.
I find this kind of bizarre because you can look around and see how it's obviously not true. Dogs are happy as clams to just socialize with their owners / other dogs and just live. People hustling to always get to the next goal don't seem particularly happier than people who don't have a goal and just have a healthy social life.
B. The happiest people on the planet are extremely ethical, have a good moral compass and have a will to help others. They have goals and attain them. And they especially don't blame their environment for their shortcomings. They find ways to adjust their environment to themselves and not the other way around.
Someone who is content with a simple life is still following that maxim. Their goal is to live each day in relative comfort according to their own standards.
Fidelio