Back in my working years, I did short-term, back-of-the-envelope budgeting to identify surpluses I could save/invest elsewhere, whether it was a linked savings account or an investment with a brokerage firm. Unless I had a lumpy expense coming up, such as a car insurance or income tax bill, I usually had something every month I could move elsewhere. Even back in my early days of working, I still had some surpluses most months, so I rarely lived from paycheck to paycheck. After I paid off my mortgage in 1998, I was basically covering my remaining bills with one biweekly paycheck and able to save/invest the other.
Once I ERed, and biweekly paychecks became monthly dividend payments, I turned this into a spreadsheet so I could plan this out for the entire year. Most months I had surpluses although the rising cost of HI (before I got back on the ACA premium subsidy train in 2020) was making some of them disappear.
I can't imagine going through life rarely or never having these investible surpluses and barely or not able to pay my bills every month.