You just don't overspend, live well within your means.
I am on a single income of under 40k and have children. I rent (reasonably cheaply), drive a car, have wraparound childcare and am responsible for all my bills. I don't count every penny, but I am very much aware when I need to tighten the belt. I also put money into savings each month for bigger outgoings like my annual car insurance renewal. I drive a cheap and cheerful, 12-y.o. car.
Our days out are walks in the local-ish area, picnics, maybe the odd farm. Kids are entertained by old-fashioned stuff like board games, which, after the initial outlay, cost me exactly nothing. And I have a teen, too, so it's not just a case of "they don't know". I cook from scratch and use local and seasonal produce.
Two things are really important here:
I don't give a shit about status symbols, so really couldn't care less about being seen to drive an old banger, wearing last year's clothes or having a no-name phone. Therefore I also try to repair over replacing items needlessly.
While I allow my children to embrace new technology, I have also taught them things my parents and grandparents would have done for fun, therefore explored their own interests with them and brought them up to value books and family games. So neither of us feel the need to compete and it's quite funny to watch how their "cool" friends enjoy the novelty of playing something old-fashioned when they come and visit.