I can't stress enough to young people how powerful it is to leverage your low fee, company provided 401K plan from an early age. I have gone higher for periods of time, but for the most part just contributed the percentage of my pay that maximized the company match. For me, that is 5% which the company then matches with 3% of annual pay. In addition, they contribute 7% of annual pay to every employee at end of year (my company pays a lower base salary than competitors but I like this 7% I never see going straight to savings on top of base salary). So at a minimum, 15% of my annual pay into the 401K plan every year. I'm 49, I married at age 32, my wife is 3 years younger and works (but only 1-2 days a week from when the first of our 3 kids were born until 4 years ago and now 4 days a week), I'm a spender, have no side hustles or businesses, and I still have a $2 mil net worth (although $500K of that is from house equity). I am far from the incredible saver or investment manager that many on this thread appear to be, and my net worth may not compare - but I am on track for a comfortable retirement and that's all I wanted. Never chased wealth or early retirement but tried to balance living in the now while responsibly planning to be able to maintain lifestyle in retirement. Zero effort other than checking a box on a 401K contribution form, selecting some S&P 500 type funds, and not reacting to market scares or run ups - just let it ride. I am fortunate to have an A&M engineering degree, a decent salary, and received promotions, but the savings rate and stock market performance did the bulk of the work. Could probably retire at 60 but may work a few years more.
On top of the 401K contributions I have 95% only purchased used cars (but a LOT of them), am underhoused perhaps, and my wife is NOT a spender at all. Take care of my own yard, rarely hire a maid, do pay someone to treat pool. Lifestyle matters but as long as money is contributed to retirement fund prior to that paycheck ever getting into your bank account, and you don't take on massive consumer spending debt, you should be good long term.