Solo cooking is a challenge, especially if you like a lot of variety.
I love it when I find a place with good bread that sells half loaves!
I now purchase greens which can be used several ways:
spinach can be raw in a salad or cooked
cabbage raw in a slaw or cooked
I use my food saver and freezer a lot. And I keep a written inventory and “map” for the frozen assets.
Sounds like you were cooking for two - probably 2.5 with the amount a high school male usually has! Pay close attention to what you might be purchasing on autopilot…Rethink what might be better to purchase in smaller amounts. I buy russet potatoes by the piece. Sometimes I buy onions by the piece if it doesn’t look like I’ll be cooking every night for the next week or so. It’s fine to break off the number of bananas you want from the larger bunch!
You might want to explore frozen vegetables. It allows for more variety, less waste and the quality can be excellent.
The shopping partner idea is a good one! I used to have one. It was great to be able to split Costco purchases. We each could easily consume half a rotisserie chicken, bag of greens, etc.
I don’t use the salad bar idea as often as I should. At this point I purchase produce that keeps and supplement that with small amounts of produce with a shorter life. You can extend the fridge time with proper handling. Ex: remove mushrooms from the plastic covered tray and store in a clean paper bag in the fridge. They will last twice as long. Trim ends of herbs and cull bad spots, place in a tumbler with a little water, loosely cover with a plastic produce bag. Parsley or cilantro can last weeks for me with frequent change of water.
Keep an idea list for items that you find hard to use up. If I purchase celery for a dinner recipe I plan on making tuna or salmon salad for lunch, have celery stuffed with cream cheese for a snack, braised celery for a side dish over the next 10 days. Iceberg lettuce may be used for taco salad, lettuce wraps, add-on for sandwich or burger in addition to use as a salad. It also can be cooked!
Utilize your meat counter. If they are staffed most grocery stores will split and repackage their prepacked meats. You don’t have to order by the pound! I purchased 1/3 lb. of grind the other day - just enough for two stuffed peppers!
My stuffed pepper recipe was 1/4 of my old recipe. Original recipe called for an egg. I beat the egg then spoon off 1/4 of it. The rest can be put in Tupperwear and added to another egg for scrambled eggs or an omelet the next day.
I do find I’m prone to a certain amount of apathy when cooking for just me. Cooking for others motivates me to plan and experiment due to their enjoyment and the fact that I can use up food faster. To combat this I try to plan special meals and find kitchen projects that work for a solo eater. Pickling and fermentation are good. You can explore, learn and the results last a good while.
I belong to a cooking Meet-up group. Get together potlucks are themed, usually ethnically. It’s an opportunity to try new recipes, eat a wide variety of dishes and enjoy good company. It’s a nice to chance to bake since it is hard to bake treats for just one. Not impossible, but tricky.
Keep notes and track what works and what doesn’t. It takes a while to find the system that works for you. When I’m in a slump the WFD (what’s for dinner) threads can be very inspiring. There are several solo cooks and many cooking for two - lots of ideas to spin from!