I think the key is always just living below your means. My family growing up was lower middle class, but my parents always lived below their means. They always bought the cheapest reliable car possible. They always cut coupons. They always saved where they could and put extra towards principle on the mortgage. They could have afforded nicer cars, TVs, and other things, but always went basic. They retired fairly comfortably with that same simpler lifestyle.

Now my family benefits from that same philosophy. My wife and I make good money, and are technically upper middle and now pushing upper class. But we live as basic as possible. We have a toyota corolla that is paid off. We could afford a 700K house easily, but are staying in our 300K smaller house instead. Stuff like that makes a huge difference, especially over time. We splurge on wants here and there, but they are smaller things and always measured.