Jefferson's warning cuts deeper than simple prudence—he's identifying a peculiar modern vice, the conflation of future earnings with present wealth. The danger isn't merely overspending; it's the psychological shift that happens when we treat tomorrow's paycheck as today's permission slip, a habit that transforms ambition into entitlement. Someone working toward a promotion might justify new furniture or a fancier car as already deserved, only to discover that life's uncertainties—illness, job loss, market shifts—won't honor such provisional claims. The wisdom lies in recognizing that money unearned remains entirely speculative, no matter how confidently we expect it.