I don't think I have made any shoe mistakes the last year.
A couple of years ago, I noticed that my feet size had changed a little with age, so since then I have bought shoes that are slightly larger than those I used to buy. And I have promised myself that I'll will never again wear shoes which feel uncomfortable.
In the last year, I got rid of several pairs which either were too small or just looked worn out. I evaluate my shoe wardrobe at the beginning of each new season (= 4 times a year). And sometimes, I even shop months in advance if I see items I know I need, for instance as replacements of worn out items. Three weeks ago, I saw, and tried on, a roomy pair of lined winter boots which I liked so much that I decided to buy them immediately, though I would probably not need them before late November (but by then, these darlings may be sold out). In the meantime, I have been invited to join a friend for a special trip to a very beautiful but cold place, so lucky me am now packing my new winter boots and other warm stuff--we will leave in two days.