The buffer, and what it is for

Build a small buffer early — the cost of a broken laptop, a flight home, a deposit you did not expect. It does not have to be large. It has to exist, because the alternative when something goes wrong is high-interest borrowing at the worst possible moment.

Build it in the first weeks when money feels plentiful rather than at the end when it does not. And define once, in advance, what counts as a reason to use it — a buffer with no rule attached quietly becomes ordinary spending money by November.