6. Change the trip, not just the list
The final habit is about the shape of the shop itself, and it is the one that quietly undoes the other five when people get it wrong.
Go less often. Every trip carries an overhead of unplanned items — the average is a handful per visit regardless of how disciplined you are. A household shopping four times a week pays that overhead four times. One main shop plus one small top-up for fresh produce cuts it roughly in half, and it forces the planning in step two.
Never shop hungry, and this is not folklore: hungry shoppers buy more calorie-dense, higher-margin items and they buy more of them. Eat something first, even if it is an apple in the car park.
Take a list and hold to it, with one deliberate exception. Allow yourself one unplanned item per trip — a clearance bargain, something someone in the house has been asking for. A rule with zero flexibility breaks; a rule with one sanctioned exception holds for years.
Consider online delivery for the main shop, especially if impulse buying is your weak point. The running total sits on screen as you build the basket, previous orders make the list nearly automatic, and you never walk past the bakery. Delivery fees of $5 to $10 or £3 to £6 are often less than the impulse spend they prevent, and many chains offer a monthly delivery pass that pays for itself at one shop a week. Check the substitution settings before you order, and refuse substitutions on anything where a swap would change what you cook.
Finally, track the total for one month only. Not forever — one month. Write down each shop’s total in a note on your phone. The number itself changes behaviour more than any budgeting app, and after four weeks you will know exactly which of these six habits is worth keeping in your house and which one you can drop.