I love DD, but I was also desperate to get back to work and adults when she was a baby. I'm not terribly cut out for all that "mother earth" stuff on a 24/7 basis (although we had the cloth nappies, I do an awful lot of cooking from scratch, she's a great baker having learned at my knee, etc etc). And I had a great opportunity to do a 2 year Masters starting when she was 9 months old.
As it happened, she was also a "hard" baby - which we didn't realise as she was our first and also first in extended family. Between silent reflux as a baby, and Aspergers/ADHD being diagnosed in senior infants (equivalent of P1 I think - 2nd year of primary school), it was (and still can be) full on.
With our jobs and our lives, I don't think we could have managed a 2nd, and I certainly wouldn't have wanted to give up work. And at this stage, we are happy chuntering along.
DD has started secondary school this year. Because we have enough money, she has done mostly any afterschool activity she wanted and tried out lots in the ECA programme at primary school. She was in various sports clubs and is doing most of those sports still through school (may go back to club hockey if life gets slightly less hectic), and is a very active Scout as well. She started sailing as a full-day summer camp activity (most around here finished at 2pm - not great for working parents!), and we found it was not only something she enjoyed, but she started to communicate so much better because of it (no "need" to talk when they arrived, but they had to talk to each other on the water about who was pulling what rope and going where and avoiding crashes - so by the time they got off the water, she was chatting to others).
We have been able to give time, attention, and money when needed, to various supports to help her achieve her potential and overcome some of her difficulties.
But we've also been able to continue to work hard, both of us, including having to travel internationally and get promoted further. And do some fun stuff, on occasion, for ourselves. And while it's occasionally more hassle than a family of 4, it has been a good number for holidays and adventures - hiking in mountains, a couple of city-break weekends, "big" holidays for "big" birthdays etc. And the ideal number for a row on a plane!
And she has some very good friends locally, and DCousins as well, so hasn't really missed out by not having siblings.