I definitely related to this good (albeit lengthy) article in The Atlantic. It is a special experience being single past the age of 35, but it doesn't have to be hell. There's a lot packed in the article (lots of academic theories on whether or not the marital landscape is shifting) so I'll highlight what resonated for me:
"I definitely noticed an increase in my own contentment when I began to develop and pay more attention to friendships with women who, like me, have never been married. Their worldviews feel relaxingly familiar, and give me the space to sort through my own ambivalence. That’s an abstract benefit. More concretely, there’s what my brother terms our 'immigrant bucket brigade'—my peer group’s habit of jumping to the ready to help each other with matters practical and emotional. This isn’t to say that my married friends aren’t as supportive—some of my best friends are married!—it’s just that, with families of their own, they can’t be as available."