Lifestyle creep, in numbers

The pattern is well documented and quietly expensive: pay rises, spending rises to meet it, and the saving rate never moves. Ten years and several promotions later the person earning three times as much is saving the same proportion of nothing much.

The counter is mechanical rather than moral. Decide in advance what share of any raise gets absorbed and what share is set aside before you see it, and automate the second part on the day the raise starts. Deciding once, early, beats deciding every month with the money already in the account.