How do I work out what enough is — and stop there?

You want to know what enough is and stop there. Notice what happens without a stated number: enough is always slightly more than you currently have, which means it can never be reached. That is not a flaw in you. It is what happens to any target defined by comparison. There is no greater misfortune than not knowing when you have enough. First, write the number down. The salary, the hours, the size of the thing. A number on paper can be reached. A feeling cannot. Second, write what the number is for. Enough is not a quantity on its own; it is the quantity that buys a particular life. Without the second half, the first half drifts upward every year. Third, decide now what you will do when you arrive, because arriving without a plan feels like emptiness, and emptiness gets filled by setting a new target. This is the step almost everyone misses, and it is why so few people ever stop. Fourth, hold the number for a year before revising it. Revision on a good month is not revision; it is the drift wearing a reason. What is your number, and what is it for?