The happiest mothers I know are those who are single, but have shared care with their ex, and their ex looks after their DC properly. I know a few mothers like this, and they all say their ex does way more than they did when they were together, plus they get lots of time off to pursue friendships, and hobbies. These mothers tend to socialise lots, and maybe because they get so much time off, seem way more relaxed when their kids are badly behaved, than the rest of us.