Let's be very clear on what grocery shopping for yourself means. That doesn't mean that you walked into the store, put things in a cart, paid, and left. That's the easy part. Sticking to a plan as loose as that means you're going to walk out with beer, some sort of cheese cracker, Hungry Man frozen dinners, and a magazine you'll masturbate to even though you have the internet. By grocery shopping, we mean knowing what's essential and shopping for those items at the right prices.
A lot of learning how to grocery shop just comes from being broke. When you're broke, no one's buying anything for you, so you have to choose. Then once you choose, you realize that your choices are limited to anything under a dollar. That's why it's so upsetting when you go grocery shopping at the dollar store and you see an item for $1.50. Why are you trying to play me?