It's a good question and you do just do it, you do just plod on. You make sacrifices and don't do stuff/buy stuff yourself. (I am talking about myself and DH here, and other people like us who have always been average earners.)
We would not buy new clothes unless we needed them, we hardly went to the pub, we did our own hair at home (whilst our 2 DD went to the hairdressers,) we had a cheap £10 PAYG phone from Argos, and we shopped for clothes (when we did buy them) in Primark and Peacocks. DD had theirs from New Look, Next, and H & M.
We did splash out on holidays, and went abroad around 10 times when they were 5 to 15, but that was with the kids, so they got the benefit of that too.
They are a year and 2 months apart, so it was hard going, and especially when they were at uni. They had part time jobs and uni loans, but both constantly needed more money.
We just got used to having very little. We went on holidays as I said, and had day trips to the beach, and to the zoo, and theme parks and the like, but again, it was 'for the kids' and with the kids.
They left uni in 2017 (both together as the older one started a year later, as she wanted a year out,) and they left home too, and got jobs fairly quickly. So long story short, we have not been supporting them in any way for 4 or 5 years now.
Although we are not massively high earners, (just average,) we are constantly shocked at how much money we have left at the end of each month now.
Sorry, I don't want to sound braggy, and as I said, we had nothing for ourselves for the 21/22 years, as we were supporting/paying out for 2 children very close in age.
Just trying to illustrate the point, that children cost a bloody fortune, and I sometimes wonder how we did it! (And you WILL notice when they leave home, how much more money you have!)
I would never change a thing obviously, and both myself and DH love our 2 daughters to bits, and they are the best thing to happen to us. And we now have 2 mid 20-something, wonderful, intelligent, hard-working successful young women for daughters. But I'd be lying if I said we didn't sacrifice quite a bit, and that they didn't cost a fortune!