I'm convinced that one of the keys to Foreign Service happiness is a portable hobby. When you move countries every few years, it can be exhausting to start from scratch with a new pastime every time, especially knowing there's no guarantee you'll ever be able to do it again. Many of the happiest folks we've seen with this lifestyle have a hobby they can take with them (at least almost) anywhere.
For us, having these hobbies no matter where we go helps wherever we are feel like home a little sooner. We have a few fitness-related ones: M plays soccer, the most popular sport in the world, and I can always fall back on Blogilates YouTube videos, which I can do from the comfort of our home even if I don't have access to a gym or any equipment. I've learned the hard way from previous experiences living abroad that fitness is not a universal recreational activity, especially for women. I've lived in places where it was impossible to go running because of weather or crime or cultural sensitivity, or where the gyms were almost completely reserved for men. It can be that much more difficult to adjust to a "normal" life somewhere where you can't find a way to break a sweat.
On top of those, we can count on certain categories of entertainment made possible with modern technology like Netflix, video games, and e-books. (After all, in a lot of countries, just finding recently released print books can be a challenge.) As I type this, I'm watching M work his way through the Kingdom Hearts series on PlayStation (one of my childhood favorites I'm so grateful we can enjoy in Kenya).
In a mobile lifestyle like ours, these hobbies can be the difference between unbearable homesickness and relative comfort. Although it's fun to try new and exotic things, I'm a firm believer in finding the balance between adventure and stability - where we've found that commitment to knitting or board games or photography or whatever it is can really come in handy.