If a person is not made to have a constitution of walking, their legs will lose strength and the whole body will become weak.
If you do not develop a constitution of writing, you can only speak but cannot write what you have said.
For someone who required exactly six hours of sleep per day to remain healthy, if they develop the constitution of sleeping just three hours a way, then they are healthy only if they sleep three hours. This is what it means to have developed a constitution.
The body, brain, and heart of human beings depend on how they are made. They depends on how they are trained.