The actual universal advice is "use that difference to pay down your existing debt, highest interest rate first. Then, after that stops being worthwhile, put yo

The actual universal advice is "use that difference to pay down your existing debt, highest interest rate first. Then, after that stops being worthwhile, put your money at work." Special cases may apply - you always want a rainy-day fund, no matter what (even just the lack of stress around finances that comes with not living hand-to-mouth makes it a no-brainer) and some debt should perhaps not be paid off immediately - but I'm pretty confident that the gist is correct.