Wow, this was cool to read! I definitely use the goal of the project to motivate myself to learn how to complete it, but I never realized it until you laid it out. I understand what OP says about the skill "sliding off" but the project is usually complete before that happens and only becomes an issue on revisiting it later. Like my Magic Mirror project that I completed but it's using the Pi and some software that I don't remember now. But the mirror is still great, hooked up to a PC with wallpaper engine running.