In the macroscopic world that we observe in everyday life, objects and people do not typically exhibit the strange quantum behavior seen at the microscopic level. This is because macroscopic objects are composed of an incredibly large number of particles, and their behavior is governed by classical physics rather than quantum mechanics. The principles of classical physics, such as Newtonian mechanics and electromagnetism, provide accurate descriptions of the behavior of macroscopic objects.
The phenomenon you mentioned, where macroscopic objects do not pass through walls or disintegrate, can be explained by the stability and interaction of atoms and molecules. Atoms are composed of a nucleus (containing protons and neutrons) surrounded by electrons. The electromagnetic forces between these particles hold the atoms together and determine the structure of solid objects.
The electromagnetic forces act as a repulsive barrier that prevents particles from passing through each other. When you try to walk through a wall, for example, the electromagnetic forces between the atoms in your body and the atoms in the wall repel each other, preventing you from merging with the wall. This repulsion is a consequence of the electromagnetic interaction described by classical physics.
Quantum decoherence, on the other hand, is a process that describes the loss of quantum coherence and the transition from quantum behavior to classical behavior. It refers to the interaction of a quantum system with its environment, leading to the emergence of classical-like behavior. In macroscopic objects, the interactions with the environment are so numerous and complex that quantum coherence is rapidly lost, and classical behavior emerges. This is why we don't observe quantum phenomena on a macroscopic scale in everyday life.
So, the stability of solid objects and the absence of macroscopic quantum effects are primarily due to the interplay of classical physics, such as electromagnetic forces, and the loss of quantum coherence through interactions with the environment.