Cancel one subscription you forgot you had. Not for the money — for the proof that you're paying attention again.

The thought behind it

Behaviour beats intention here. The line describes a lever, and levers do not care how motivated you feel. Money Mind reads a balance as evidence of decisions rather than as a score, which is the harder thing to look at. The line turns on “one” — remove that single word and what is left is advice you have already ignored.