If you've lived in your house/apartment for a good long while and settled in, you have an idea of what it was like to use Classic Mac OS 9 (and earlier).

It's like flicking a lightswitch or reaching into a drawer and grabbing a spoon without looking. Everything is always right where you left it. Double-click a folder and the window opens in exactly the same state that you left it when it was last closed. All the icons are arranged in the same way, with the same label colours you gave them, and each of the folders inside that folder open the same way as well. One folder might open in list view sorted by Date Modified while another opens in icon view with the exact arrangement you decided on, all according to the way you left them.

All of those folders open their windows in the exact same position, size, and shape they had when you closed them. This lets you quickly drill down through layers of nested folders, moving your mouse to the next one before your eyes can even register it on screen.

The effect of this extreme level of persistence is that you develop muscle memory for the mouse. No other operating system environment I have ever used works like this, or at least this pervasively (modern macOS still has this for the menu bar). Everyone else just gives up and relegates the muscle-memory control to the keyboard only. This is a huge tragedy! A Classic Mac OS power user works with one hand on the mouse, one hand on the keyboard, and uses muscle memory with both to fly around the UI and work very efficiently. This is especially valuable when you're working in software that needs the mouse anyway, such as art or design software.