I hate shopping for many reasons; all the people, the brightness, the noise, too much choice of stuff in too many different colours etc.
To avoid too much anxiety, I have to know exactly what I'm going to buy, exactly what brand, and exactly where I can find it in on the shelves. I try to pick a time which will be as quiet as possible, and I only generally shop at places within walking distance, so that I don't need to use public transport. Then, if all goes well, I'm in and out as quickly and stealthily as possible.
That all helps with the anxiety, but it does mean that my shopping habits are extremely repetitive, and thus, so is my diet. If something I wanted to get isn't available, I go totally to pieces because I can't decide on an alternative, and end up wandering aimlessly for a while or staring at a shelf of stuff, frozen there like a human statue. By always using the same shops, at least the store security learn to leave me alone after a while, but I've been refused the sale of alcohol sometimes because I look so erratic.
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When you are fighting an invisible monster, first throw a bucket of paint over it.