How do you cope with desperately wanting something you probably won't get?

It could be anything, a better car, better house, a raise, a specific pet, etc…

For me, it’s that I desperately want another baby but my husband doesn’t. He used to tell me he wanted four kids, now he says he’s fine with two and doesn’t want to start over with another newborn because he’s too “old”. He’s 34, lol. I know he doesn’t want another child, but I really do and it makes me feel incomplete, somehow. I’m having a hard time coping with it.

What do you want that you can’t have? And how do you move on from the feeling that you’re missing something?