You can make a one-time purchase like a water filter or a filter bottle and use that going forward.
Stick to the items that you wanted to buy in the first place. Only make use of the sales if it is something that you need.
I am often buying more stuff when I have a big shopping cart compared to when I have a smaller basket.
Another smart thing grocery stores do is change their entire store layout periodically. This increases the chance of you buying something extra for the stores.
When you’re buying food out of season, the prices are seriously more expensive.