Part of nourishing yourself is buying food to eat, and that often happens at the grocery store (and/or the farmer's market!) Do you:
A. make a list, and stick to it
B. go free like a bird and grab whatever looks good to you in the moment
C. combination of the two - you go with a list, and leave with much more
What works for you?
This may not be surprising, but for most people, making a list means chances are high that you'll make choices at the grocery store that your bank account and belly will appreciate.
Making a grocery list is a practice in mindfulness.
When you take the time and attention to think about what you want to eat ahead of time, you can check in with your body from an observer's perspective. You had pizza last Friday and went to sleep with a stomach-ache = maybe no pizza this week. You had salad for lunch last week, but you were hungry by 2pm = maybe you need to add more fat and protein to this week's lunch, so you put chicken and avocados on the list. If you don't give yourself the gift of reflection and forethought, you run the risk of being on food-autopilot. (No one wants that!)
Unless you grocery shop daily, going without a rough idea of what you need means the majority of what you buy will be what you want to eat at that time; not necessarily what you're going to want in a day or two. If you're super stressed, that could mean lots of refined-sugary-snacks or salt-laden-supplies. If you're very hungry, it could mean buying a lot more than you'll actually use (that's when your bank account gets sad.) Or maybe the opposite - if you're beating yourself up for something you ate last night, you could end up not buying enough, and then you end up ordering takeout in a few days because there's nothing in the house...The scenarios are endless clearly.
If you have a rough idea of what you're going to cook this week, you can make sure you at least get the ingredients to make those things, and then if something else catches your eye (baby pineapple, anyone?), maybe you grab it, maybe you don't. But the list is grounding - it's something you can come back to.
Do an experiment: if you don't normally, try making a list before you shop this weekend.
You don't necessarily have to write it on paper; I usually use a 'notepad' on my phone. Use what makes sense for your personality/lifestyle!