I have 2 boys, I always wanted 3. My first thought after having DS2, was please god don't let this be my last baby.... hormones!
Anyway, DH only wanted 2 and we both have full time careers with no options of part time (overseas).
I asked him to let me come to terms with it in my own time. I didn't want to have any more babies after 38, and I didn't want to have too big of an age gap between the 2nd and 3rd.
Now here I am, with and 8 & 5 year old and I'm so glad we didn't have another. My boys are best friends, they love each other, and we can give them one on one time.
And the biggest thing for me is that I no longer feel like there's anyone missing.
It takes time I think. Some people never get over that yearning for another and I'm very glad that my feelings went away because they're agony. The eternal broodiness takes over everything else. But whilst my heart remains a little wistful for a newborn baby placed in my arms, the head knows the reality and it's not for me.
In fact, I'm pretty sure if I had a scare now (I'm 40), my immediate thought would be "fuck!!"