pharmakos
Bluelighter
This is very interesting. It makes me think of how your perception tends to continually adjust to new situations. You can try to improve your life, but any improvement you make quickly loses its novelty, and becomes absorbed into your frame of reference. So you're always measuring things relative to where you stand now - no matter if you're an impoverished third-world peasant, or a lottery winner becoming bored with all the easy money, your life now is the same mildly uncomfortable existence, and happily-ever-after is always just around the corner.
Kind of like how your retinas adjust to a bright light.
And that continues until you learn to just accept whatever you have, and appreciate it for what it is.
sounds like the Hedonic Treadmill
The hedonic treadmill, also known as hedonic adaptation, is the supposed tendency of humans to quickly return to a relatively stable level of happiness despite major positive or negative events or life changes.[1] According to this theory, as a person makes more money, expectations and desires rise in tandem, which results in no permanent gain in happiness.