For a few years I was a more or less by-the-book, practicing Orthodox Jew. I'm not going back there. It's just too crazy, and it makes me too crazy. My natural level of neurosis does not need any extra help. These days, I keep "ingredient kosher" but I eat (vegetarian) pretty much anywhere I like. Give up eating out, except in certified kosher restaurants? Not gonna happen.
And don't get me started on all the stuff around sex and gender.
But, Shabbat? It's been years since I really gave it a serious effort, and I find I'm missing it. When you first hear about all the rules for keeping Shabbat, you think, "ARE YOU PEOPLE OUT OF YOUR F***ING MINDS?" (It's OK. Everybody has that reaction.) And the rules seem weird and crazy. But I've come to appreciate the geekiness of it all.
For me, the key is in understanding Shabbat as an exercise in non-attachment. "The sage goes about doing nothing, teaching no-talking." (Tao Te Ching, ch. 2.) "Therefore the way of freedom is not inaction, but to cease from identifying oneself with the movement and recover our true identity in the Self of things who is there Lord." (Sri Aurobindo on the Isha Upanishad.)
Shabbat provides a resolution to the problem: How to control that sense of attachment to the fruits of our work, while still living in the world? How to achieve non-attachment without renunciation? The solution offered by Shabbat is a very down-to-earth, practical solution - in other words, a very Jewish solution. We get all our "stuff" done in six days, and set aside the seventh as a day of non-doing. It is true that mainstream Jewish practice doesn't have a strong tradition of contemplative meditation; but I'd like to suggest that Shabbat itself is a subtle, prolonged form of meditation.
Another thing that sometimes gets overlooked is that the commandment to keep the Sabbath is also a commandment to work: "Six days shall you labor, and do all of your work ..." In fact, the verb "to labor" also means "to serve". And I've found that practicing the observance of Shabbat makes me more aware and involved during the week.
Then there's also a sense of liberation in keeping Shabbat - a sense of being your own boss. And I like that too - and I've missed it.