My grocery shopping system failed because I followed common advice

I set up a detailed meal plan to cut food waste and save money. Everyone says planning meals ahead stops impulse buys. But I found it too strict when my schedule changed. For example, if I worked late, my planned ingredients went bad. This meant I threw out food and still ordered takeout. I learned that rigid plans don't work if life is unpredictable. What methods work for you when plans need to bend?