Activation and effort intrinsically create toward the organism the signal which makes improvement possible. This has an obvious reason; the organism is like a machine that was created with energy optimization as a priority and at the same time necessity. To think is an activity that consumes energy, and, sometimes, when the brain doesn't reclaim it, it's logical that the organism tries to optimize the energy consumption without providing special priority to this kind of function.
It's then more important to store it or use for other purposes. This is another example of how Nature always provides examples of the best engineering. So far, so good, nothing to complain. Although, really?
Deactivation and accommodation has the counterpart of being antagonistic to the improvement. With other words, who doesn't maintain his/her mental or physical condition in an adequate degree of motion works against his/her own capabilities even causing gradual atrophying.
Like an award for workers or a punishment for vagrancy, the everyday actions and especially the attitude is really what creates enormous differences between human beings. Another topic is that never is too late to leave deactivation, accommodation routines and start other ones that for sure cause a betterment of psychological and physical capabilities.
From here, we recommend picking up those areas that permit a long journey like science, music and other fields of art principally. There's room to an entire life of constant training in each one of these. For physical condition, sport goes also for a long time.
The best experiences come after long years of training; any person should discover it by themselves!