In my experience, the best way to learn how to feed yourself is to become addicted to learning how. Food blogs are so good at this - even if you don't copy any recipes directly, when you peruse through blogs, (or youtube channels, or any other type of food media) you're absorbing. You're being showed what is possible. This information will give you the confidence and motivation to start cooking, or if you're already deep in the cooking game, it'll get you to mix it up and try some new things.
Here are a few of my favourite food blogs and food media:
Chocolate Covered Katie - Healthy vegan desserts! Holy fuck, is this ever useful if you have a sweet tooth. One of the things I've learned is that I usually find cupcakes and donuts and most sweets you can buy.. well.. too sweet. Recipes here are healthy-ish, not too sweet, and very easy. There are some really cool single-serving recipes for when you just need a bit of cake, or just one cookie.
This Rawsome Vegan Life - This site has insanely beautiful pictures. I've read this blog for hours, and I've learnt so much about the possibilities of raw food, but I don't think I've ever actually used a recipe from it. And that's A-okay! Part of the appeal of this blog is the author, (who is pretty young, like highschool maybe?) talking a lot about her experience as someone who only eats raw food, being confident in her choice to nourish her body this way, and just her general fearlessness. I can't emphasize enough how gorgeous her pictures and food presentation are. It'll make you drool.
Two Greedy Italians - Let's switch gears. I love vegan food, but I'm not vegan. I like to combine the veggie goodness of vegan food with high-quality meat and dairy products. Last year, I taught myself how to cook by starting with vegan food, because it's a lot harder to poison yourself when you aren't cooking meat. My tummy's gaze has shifted onto traditional foods like broths, offal, stews and sprouted grains. This is where Two Greedy Italians comes in. It's an entertaining and special little series about two old Italian men, who are old best buds and just go around Italy eating and cooking amazing traditional food. They feed each other pieces of cheese and get in arguments and they love each other and they love ingredients and processes. You can almost taste their pizza and smell the cheese. They show you how to cook it, too. A big thing that I took away from watching this show is the importance of food rituals, taking time preparing meals, making it a priority, eating and drinking with those you love, and always enjoying dinner with some wine. Also, it's all on YouTube!
The Internet is huge. Explore around and find something that sparks your interest and captures you. If you're in a cooking rut of some kind, always remember that education is motivation. If you're eating a ton of junk right now and trying to snap out of it, use Google to learn the facts about processed food, vegetable oils and sugar.
On the other hand, maybe you're an incredible cook, but you want to get better at grocery shopping. My advice is to try to step away from buying ingredients for specific dishes. Fill your cart with nourishing food that you love. The goal is to flow with that food throughout the week, piecing together ingredients to make inventive meals. Get inspiration through recipes, but don't worry about following them. Teach yourself how to improvise. Sometimes these meals will fail, and possibly be inedible. That's what pizza delivery was invented for. I know this from experience.
Whatever it is that we want to improve about the way we eat food, Google almost always has the answer. Sometimes I think we just don't bother searching.