” Is there a real basis for this, is there something that does not change?”
There is NOTHING in this world that does not change.
It depends on exactly what you are trying to change.
Once you figure that out, you need to figure out what MUST BE changed in your THOUGHTS, SPEECH, and ACTIONS that could lead to the change you are seeking.
If you found out the right causes, AND if you follow through what MUST BE done, then the change will happen OVER TIME.
P.S. I was thinking about this a bit more.
- A material thing like our body can be “improved” to some extent only up to the middle age. After that one cannot reverse the inevitable decay with time.
– Basically everyone knows what to do to make a physical body “better”: exercise and eating well. - Our minds (and thus the progress on the Path) can be changed for the better for a longer time. But when one gets to really old age, the brain (which is physical) starts decaying and that will make any more progress impossible.
– The basic suggestion by the Buddha to make one’s mind better is to remove lobha, dosa, moha from one’s mind.