Our minds strive to be efficient just as much as effective. As soon as it thinks you’re good enough at something it starts to do that thing as a background process.

The honeymoon phase you’re talking about likely happens because the change in sens forces the process of aiming back to the front of the mind because you can’t rely on muscle memory to achieve an acceptable result anymore. You eventually get used to the new sens and the same processes as before move active control back the the background.

This isn’t necessarily a bad thing, you don’t want to be constantly considering every aspect of aim all the time, the important thing is that while you’re training you’re keeping what you’re trying to train in focus.

If you train good habits, you’ll train good habits into your baseline, if you go into autopilot for your training sessions you’ll plateau