Galina just inspired me with a comment.... :-)
She observed that diet/lifestyle tweaks often work for awhile and then cease to do so -- i'm sure most of us can agree with that! We are sailing along losing weight, or feeling better, or getting stronger, then wham, we stall -- or worse, we lose ground. And WHY (i said to myself) does this happen?
Operating your "vehicle" is very much like driving a stick-shift. In the mountains. When the wind is blowing. You can't just put it in one gear and feed it the same amount of fuel and expect things to be constant -- you have to push in that clutch while simultaneously letting up on the gas pedal, move the lever to a different position, then feed gas again while disengaging the clutch pedal. You have to speed up and slow down to deal with curves. You have to be on top of things, paying attention to what's around you and making suitable adjustments.
Our bodies are smarter than we give them credit for, and they have a very good memory. Some people can operate their properly-functioning bodies like an automatic-transmission vehicle on flat ground, using cruise control. They're constantly making little adjustments of which we're completely unaware. Have a micronutrient shortage -- they give us a craving which SHOULD take care of the problem. When illness or midlife changes up the terrain, we have to consciously manage things more -- our vehicles require us to swap over to standard-transmission, take it out of "cruise" and DRIVE.
So we have to deal with it. We have to "learn to drive a stick" unless we want to be stalled at the side of the road, because that is NO FUN. If we have to call the tow-truck because we've overheated or fouled our fuel-pump or burnt up the engine trying to get up that gradient in the wrong gear, it can get really expensive and the car might never run right again.